Allergenic proteins and peptides from dog dander and uses therefor

ABSTRACT

Isolated nucleic acids encoding allergens of  Canis familiaris , Can fI or Can fII. are disclosed. A cDNA encoding a peptide having a Can fI activity and a predicted molecular weight of about 19,200 daltons is also described. A cDNA encoding a peptide having Can fII activity and a predicted molecular weight of about 18,200 daltons is also disclosed. The nucleic acids can be used as probes to detect the presence of Can fI or Can fII nucleic acid in a sample or for the recombinant production of petides having a Can fI or Can fII activity. Peptides having a Can fI or Can fII activity can be used in compositions suitable for pharmaceutical administration or methods of diagnosing sensitivity to dog dander.

PRIORITY INFORMATION

This application is a continuation of U.S. application Ser. No. 10/196,107 filed Jul. 16, 2002 issued as Patent Number 7,026,128 on Apr. 11, 2006, which is a division of U.S. Application No. 09/374,671 filed Aug. 16, 1999, issued as Patent Number 6,489,118 on Dec. 3, 2002, which is a continuation of application Ser. No. 08/491,861 filed Oct. 27,1995 issued as Patent Number 5,939,283, which is a 371 of PCT/US93/12468 filed Dec. 30, 1993, which is a CIP of U.S. application Ser. No. 07/999712 filed Dec. 31, 1992 now abandoned, which is a CIP of U.S. application Ser. No. 08/156,549 filed Nov. 22, 1993 now abandoned, which is a CIP of U.S. application Ser. No. 07/999,712, filed Dec. 31, 1992 now abandoned, and which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

Approximately 10% of the population become hypersensitized (allergic) upon exposure to antigens from a variety of environmental sources. Those antigens that induce immediate and/or delayed types of hypersensitivity are known as allergens (King, T. P., (1976) Adv. Immunol., 23: 77–105. These include products of grasses, trees, weeds, animal dander, insects, food, drugs, and chemicals. Genetic predisposition of an individual is believed to play a role in the development of immediate allergenic responses (Young, R. P. et al., (1990) Clin. Sci., 79: 19a) such as atopy and anaphylaxis whose symptoms include hay fever, asthma, and hives.

The antibodies involved in atopic allergy belong primarily to the IgE class of immunoglobulins. IgE binds to basophils, mast cells and dendritic cells via a specific, high-affinity receptor FcεRI (Kinet, J. P., (1990) Curr. Opin. Immunol., 2: 499–505). Upon combination of an allergen acting as a ligand with its cognate receptor IgE, FcεRI bound to the IgE may be cross-linked on the cell surface, resulting in physiological manifestations of the IgE—allergen interaction. These physiological effects include the release of, among other substances, histamine, serotonin, heparin, chemotactic factor(s) for eosinophilic leukocytes and/or leukotrienes C4, D4, and E4, which cause prolonged constriction of bronchial smooth muscle cells (Hood, L. E. et al., Immunology (2nd ed.), The Benjamin/Cumming Publishing Co., Inc. (1984)). Hence, the ultimate consequence of the interaction of an allergen with IgE are allergic symptoms triggered by release of the aforementioned mediators. Such symptoms may be systemic or local in nature, depending on the route of entry of the antigen and the pattern of deposition ofIgE on mast cells or basophils. Local manifestations generally occur on epithelial surfaces at the site of entry of the allergen. Systemic effects Can induce anaphylaxis (anaphylactic shock) which results from IgE-basophil response to circulating (intravascular) antigen.

The pet dog (Canis familiaris) is kept in households the world over. In houses and public schools where dogs have been kept on a regular basis, dog dander allergens can be detected in dust samples (Wood, R. A. et al, (1988) Am Rev Respir. Dis., 137: 358–363, and Dybendal, T. et al., (1989) Allergy, 44: 401–411). The prevalence of allergy to dogs as assessed by skin prick test is approximately 15% (Haahtela, T. et al., (1981) Allergy, 36: 251–256, and de Groot, H. et. al, (1991) J. Allergy Clin. Immunol., 87: 1056–1065). In one study, sensitivity to dog allergen(s) was detected in 40% of asthmatic children, even though dogs were not kept as pets in their homes (Vanto, T. and Koivikko, A., (1983) Acta Paediatr Scand., 72: 571–575).

Treatment of patients with dog allergy by administration of dog dander extracts has not proven to be as efficacious as treatment of cat allergic patients with cat dander extracts (Hedlin, G. et. al., (1991) J. Allergy Clin Immunol., 87: 955–964). As with any desensitization scheme involving injection of increasing doses of allergen(s), there are the drawbacks of potential anaphylaxis during treatment, and the possible necessity of continuing therapy over a period of several years to build up sufficient tolerance that results in significant diminution of clinical symptoms.

Dog hair and dander extracts are complex mixtures containing a number of allergenic proteins. (Loewenstein, H et al., (1982) Proceedings 11th International Congress of Allergology and Clinical Immunology. London, pp 545–548; Uchlin, T et al. (1984) Allergy, 39: 125–133: Yman. L. et. al., (1984) Int. Arch. Allergy Appl. Immunol. U, 44: 358–368; Spitzauer, S. et. al., (1993) Int. Arch. Allergy Immunol., 100: 60–67). Two allergens present in dog hair/dander have been purified using immunoaffinity chromatography. A major allergen from dog, Can fI (Nomenclature according to the criteria of the IUIS (Marsh, D. G. et. al., (1988) Clin. Allergy. 18: 201–209; Agl3 according to original nomenclature), has been partially purified by two groups (Schou, C. et al., (1991) Clin. and Exp. Allergy. 21: 321–328 and de Groot et al., supra). Both groups, partially purified Can fI was established as an allergen by CRIE analysis (Ford A. W. et. al., (1989) Clin. Exp. Allergy. 19: 183–190), and then rabbits or Balb/b mice were immunized to obtain polyclonal or monoclonal antibodies against the allergen, respectively. Immunoaffinity purified Can fI (˜25 kD in molecular weight, with a minor component ˜18 kD) which elicited a high frequency of positive skin prick tests among dog allergic patients was able to deplete 50–70% ofIgE binding to dog dander extracts in RAST (radioallergosorbent test) analysis. While de Groot et. al. did not attempt to determine any amino acid sequence of Can fI. Schou et. al. found the amino terminus of their immunoaffinity purified Can fI was blocked. Hence, no amino acid sequence of Can fI is presently in the public domain.

The presence of a second (minor) allergen in dog extract was detected by binding ofIgE antibodies to dog dander/hair extracts by several groups (de Groot et al., supra. Schou, C. et. al., supra and Spitzauer et. al., (1993) Int. Arch. Allergy Immunol., 100: 60–67). The molecular weight of a minor allergen was reported to be 18 kD (Schou et al., supra), 19 kD (Spitzauer et al., supra) and 27 kd (de Groot et. el., supra). It is difficult however to correlate these results since only one group (de Groot et al., supra) affinity purified an allergen designated Can fII (originally named Dog 2 allergen). Can fII was purified from dog dander extracts in a manner analogous to Can fI using monoclonal antibodies generated to a second allergen present in extracts (de Groot et. al., supra). Molecular weight of Can fII reported by this group as ˜27 kD was later verified to be ˜24 kD (Aalberse, R. C. personal communication). Purified Can fII allergen was found to react with IgE of only 66% of dog allergic patients. In RAST analysis, Can fII allergen was able to compete with 23% of the IgE directed against dog dander extract. The amino acid sequence of Can fII has not been previously determined.

Many patients with sensitivity to dog dander allergens are treated currently by administration of small, gradually increasing doses of dog dander extracts. Use of these extracts has multiple drawbacks, including potential anaphylaxis during treatment and the necessity of continuing therapy, often for a period of several years to build up sufficient tolerance and significant diminution of clinical symptoms. The ability to substitute compositions of at least the major dog dander allergens, such as Can fI and Can fII, would overcome several of these drawbacks. Thus, a source of pure allergen that could be provided in quantity for use as a diagnostic or therapeutic reagent and therapeutic methods that would overcome the drawbacks associated with dog dander extracts are highly desirable.

SUMMARY OF THE INVENTION

This invention provides isolated nucleic acids encoding peptides having at least one biological activity of Can fI or Can fII, protein allergens of the species Canis familiaris. Preferred nucleic acids are cDNAs having a nucleotide sequence shown in FIG. 5 (SEQ ID NO: 1)(Can fI) and FIG. 18 (SEQ ID NO: 67) (Can fII). The invention also pertains to peptides encoded by all or a portion of such cDNAs (SEQ ID NO: 1 and SEQ ID NO: 67) and having at least one biological activity of Can fI or Can fII. Also contemplated are isolated nucleic acids which hybridize under high stringency conditions (e.g., equivalent to 20–27° C. below Tm and 1M NaCl) to a nucleic acid having a nucleotide sequence shown in FIG. 5 (SEQ ID NO: 1) or FIG. 18 (SEQ ID NO: 67) or which encodes a peptide comprising all or a portion of an amino acid sequence of FIG. 5 (SEQ ID NO: 2)(Can fI) or FIG. 18 (SEQ ID NO: 68)(Can fII). Nucleic acids which encode peptides having an activity of Can fI or Can fII and having at least 50% homology with a sequence shown in FIG. 5 (SEQ ID NO: 2)(Can fI) or FIG. 18 (SEQ ID NO: 68)(Can fII) are also featured. Peptides having a Can fI or Can fII activity produced by recombinant expression of a nucleic acid of the invention, and peptides having a Can fI or Can fII activity prepared by chemical synthesis are also featured by this invention. Preferred peptides have the ability to induce a T cell response, which may include T cell stimulation (measured by, for example, T cell proliferation or cytokine secretion) or T cell nonresponsiveness (i.e., contact with the peptide or a complex of the peptide with an MHC molecule of an antigen presenting cell induces the T cell to become unresponsive to stimulatory signals or incapable of proliferation). Other preferred peptides, either apart from or in addition to the ability to induce a T cell response, have the ability to bind the dog dander specific IgE of dog dander-allergic subjects. Such peptides are useful in diagnosing sensitivity to dog dander in a subject. Still other peptides, either apart from or in addition to the ability to induce a T cell response, have a significantly reduced or negligible ability to bind dog dander-allergic IgE. Such peptides are particularly useful as therapeutic agents.

Other preferred peptides comprise an amino acid sequence shown in FIG. 5 (SEQ ID NO: 2) (Can fI) or FIG. 18 (SEQ ID NO: 68)(Can fII). In one embodiment, peptides having a Can fI or Can fII activity and comprising a portion of the amino acid sequence of FIG. 5 (SEQ ID NO: 2) or FIG. 18 (SEQ ID NO: 68) are at least about 8–30 amino acids in length, preferably about 10–20 amino acids in length, and most preferably about 10–16 amino acids in length.

Another aspect of the invention features antibodies specifically reactive with a peptide having a Can fI or Can fII activity. A peptide having an activity of Can fI or Can fII can be used in compositions suitable for pharmaceutical administration. For example, such compositions can be used in a manner similar to dog dander extracts to treat or prevent allergic reactions to dog dander in a subject. Nucleic acids of the invention and peptides having an activity of Can fI or Can fII can be also used for diagnosing sensitivity in a subject to a dog dander.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows degenerate primer pairs based on residues 9–15 and 30–37 of the mature Can fI protein used in the MOPAC technique of PCR amplification. Two internal degenerate oligonucleotide probes based on Can fI protein residues 17–24 (Dog Probe 1) and 88–94 (Dog Probe 2) are shown.

FIG. 2 shows oligonucleotide primers used in a RACE PCR protocol to obtain the 3′ portion of the Can fI cDNA. A degenerate oligonucleotide probe (Dog Probe 4) is also shown.

FIG. 3 shows primers used in an anchored PCR technique to determine the 5′ end of the Can fI cDNA. A degenerate oligonucleotide probe, Dog Probe 0, based on residues 9–17 of the Can f protein is shown.

FIG. 4 is a schematic representation of a PCR sequencing strategy used to obtain the sequence of the mature Can fI protein from both strands of amplified cDNA.

FIG. 5 is the cDNA sequence and deduced amino acid sequence of Can fI.

FIG. 6 is a schematic representation of the strategy used to express Can fI recombinant protein in bacteria.

FIG. 7 is a schematic representation of the strategy used to express Can fI recombinant protein in a mammalian cell using the pJ7L expression vector.

FIG. 8 is a schematic representation of the strategy used to insert a His6 reporter group at the carboxy terminus of the recombinant Can fI protein to aid purification of the protein.

FIG. 9 shows the alignment of three partial 3′Can fI cDNA sequences (Can fI, 2Can fI and 3Can fI). An (*) indicates that the position in the alignment is perfectly conserved and a (.) indicates that the position is well conserved. A (-) was inserted where necessary for purposes of alignment.

FIG. 10 is a graphic representation depicting the response of T cell lines from patients primed in vitro with recombinant Can fI (rCan fI) and analyzed for response to rCan fI and various peptides derived from Can fI by positivity index (% of patients who positively responded multiplied by the mean stimulation index).

FIG. 11 is a graphic representation of a direct binding assay ofIgE from a single dog allergic patient to bacterially expressed recombinant Can fI.

FIG. 12 shows Western blot analysis of four protein preparations (Lane 1: dog hair extract; Lane 2: dog saliva; Lane 3: bacterially expressed recombinant Can fI; and Lane 4: recombinant Can fI expressed in a mammalian cell culture system) probed with plasma from a dog allergic patient (#901) or with plasma from a negative control patient (#250).

FIG. 13 shows the design of primers based on a partial amino acid sequence of mature Can fII and the sequence strategy for Can fII. ( ) denotes residues which were not determined.

FIG. 14 is a schematic representation of the strategy used to clone Can fII cDNA.

FIG. 15 is a schematic representation of the strategy used to clone the 5′ (A) and 3′ (B) portions of Can fII cDNA flanking the sequence encoding a portion of the amino acid sequence (shaded) of native Can fII.

FIG. 16 is the nucleotide sequence of primers used in cloning Can fII cDNA.

FIG. 17 shows the sequence strategy used to determine the nucleotide sequence of the Can fII cDNA clones 1a, 1c and 1j. The figure depicts inserts of the cDNA clones 1a (793 bp), 1c (791 bp) and 1j (774 bp). The hatched bars represent coding sequence. The triangles indicate the position of an initiator methionine codon (ATG); the codon specifying the N-terminal amino acid residue of the mature protein (START); the position of a termination codon (STOP); and the position of a polyadenylation signal (As). The arrows indicate the extent and direction of the sequencing reactions.

FIG. 18 is the cDNA sequence and deduced amino acid sequence (from Clone 1c) of Can fII.

FIG. 19 is a comparison of the deduced amino acid sequence of Can fII based on the cDNA sequence of clone 1c and a portion of the native Can fII determined by protein sequencing of the N-terminus. The amino acid residues of a signal peptide are numbered −19 to −1.

FIG. 20 shows northern analysis of mRNA of different dog tissues. Total cellular RNA (25 mg) from dog tongue epithelial tissue, parotid salivary gland, skin, mandibular and submaxiliary glands, liver and spleen was subjected to Northern analysis using Can fII cDNA as a probe. The position of RNA markers are indicated in kilobases (kb).

FIG. 21 is a comparison of the amino acid sequence of Can fII with homologus proteins MUP 6 Mouse and Rat A2U. The alignment was made with GeneWorks program. The signal sequences are underlined. Amino acid residues which are identical in all three proteins are boxed.

FIG. 22A–G are graphic representations of a direct binding assays of human IgE binding to native Can fII and recombinant Can fII.

FIG. 23 is the nucleotide consensus sequence among cDNA clones 1a, 1c and 1j encoding partial or full length Can fII.

FIG. 24 is a graphic representation depicting the response of T cell lines from 12 patients primed in vitro with recombinant Can fI (rCan fI) and analyzed for response to rCan fI and various peptides derived from Can fI by stimulation index. A stimulation index equal to or greater than two times the background is considered “positive.”

FIG. 25 is a graphic representation depicting the response of T cell lines from 12 patients primed in vitro with recombinant Can fI (rCan fI) and analyzed for response to rCan fI and various peptides derived from Can fI by mean stimulation index for the group of patients with positive responses to the peptides.

DETAILED DESCRIPTION OF THE INVENTION

This invention pertains to isolated nucleic acids encoding peptides having at least one biological activity of Can fI or Can fII, allergens of the species Canis familiaris. Preferably, the nucleic acid is a cDNA comprising a nucleotide sequence shown in FIG. 5 (SEQ ID NO: 1) (Can fI) or FIG. 18 (SEQ ID NO:67) (Can fII).

The cDNA shown in FIG. 5 (SEQ ID NO: 1) encodes a Can fI peptide which includes a 26 amino acid leader sequence encoded by base I through base 78. This leader sequence is not found in the mature Can fI protein, which is encoded by bases 79 through 525. The deduced amino acid sequence of Can fI based on this cDNA is also shown in FIG. 5 (SEQ ID NO: 2). The cDNA encodes a mature peptide having a predicted molecular weight of 19.2 kDa, with a pI of 5.53 and a single potential N-linked glycosylation site. A culture of E. coli transfected with an expression vector containing the cDNA encoding Can fI was deposited under the Budapest Treaty with the American Type Culture Collection on Dec. 22, 1992 and assigned accession number 69167.

The cDNA shown in FIG. 18 (SEQ ID NO: 67) encodes a Can fII peptide which includes a 19 amino acid leader sequence encoded by base 195 through base 251. This leader sequence is not found in the mature Can fII protein, which is encoded by bases 252 through 734. The deduced amino acid sequence of Can fII based on this cDNA is shown in FIG. 18 (SEQ ID NO: 68). The cDNA encodes a Can fII peptide having a predicted molecular weight of 18.229 kDa, with a pI of 4.54 for a mature recombinant Can fII protein and a pI of 4.44 for a full length (including singal sequence), recombinant Can fII protein, and a single potential N-linked glycosylation site. N-linked glycosylation may increase the molecular weight of the peptide and may alter the pI of the mature protein. A culture of E. coli transfected with an expression vector containing the cDNA encoding Can fII was deposited under the Budapest Treaty with the American Type Culture Collection on Dec. 29, 1993 and assigned accession number XXXX.

Accordingly, one aspect of this invention pertains to isolated nucleic acids comprising nucleotide sequences encoding Can fI or Can fII, fragments thereof encoding peptides having at least one biological activity of Can fI or Can fII, and/or equivalents of such nucleic acids. The term nucleic acid as used herein is intended to include such fragments and equivalents. The term equivalent is intended to include nucleotide sequences encoding functionally equivalent Can fI or Can fII proteins or functionally equivalent peptides having an activity of Can fI or Can fII. As defined herein, a peptide having an activity of Can fI or Can fII has at least one biological activity of the Can fI or Can fII allergen. Equivalent nucleotide sequences will include sequences that differ by one or more nucleotide substitutions, additions or deletions, such as allelic variants, and will also include sequences that differ from the nucleotide sequence encoding Can fI or Can fII shown in FIG. 5 (SEQ ID NO: 1) or FIG. 18 (SEQ ID NO: 67) due to the degeneracy of the genetic code. Equivalents will also include nucleotide sequences that hybridize under stringent conditions (i.e., equivalent to about 20–27° C. below melting temperature (T_(m)) and about 1M salt) to the nucleotide sequence of Can fI shown in FIG. 5 (SEQ ID NO: 1) or Can fII shown in FIG. 18 (SEQ ID NO: 67).

Peptides referred to herein as having an activity of Can fI or Can fII or having a Can fI or Can fII activity are defined herein as peptides that have an amino acid sequence corresponding to all or a portion of the amino acid sequence of Can fI or Can fII shown in FIG. 5 (SEQ ID NO: 2) or FIG. 18 (SEQ ID NO: 68) which peptide has at least one biological activity of Can fI or Can fII. For example, a peptide having an activity of Can fI or Can fII may have the ability to induce a response in Can fI or Can fII restricted T cells such as stimulation (e.g., T cell proliferation or cytokine secretion) or to induce T cell non-responsiveness. Alternatively, or additionally, a peptide having an activity of Can fI or Can fII may have the ability to bind (to be recognized by) immunoglobulin E (IgE) antibodies of dog dander-allergic subjects. Peptides which bind IgE are useful in methods of detecting allergic sensitivity to Can fI or Can fII in a subject. Peptides that do not bind IgE, or bind IgE to a lesser extent than a purified, native Can fI or Can fII protein binds IgE are particularly useful as therapeutic agents.

In one embodiment, the nucleic acid is a cDNA encoding a peptide having an activity of Can fI or Can fII. Preferably, the nucleic acid is a cDNA molecule comprising at least a portion of the nucleotide sequence encoding Can fI or Can fII, shown in FIG. 5 (SEQ ID NO:1) and FIG. 18 (SEQ ID NO: 67). A preferred portion of the cDNA molecules of FIG. 5 and FIG. 18 includes the coding region of the molecule.

In another embodiment, the nucleic acid of the invention encodes a peptide having an activity of Can fI or Can fII and comprising an amino acid sequence shown in FIG. 5 (SEQ ID NO:2) (Can fI) or FIG. 18 (SEQ ID NO: 68) (Can fII). Preferred nucleic acids encode a peptide having a Can fI or Can fII activity and having at least about 50% homology, more preferably at least about 60% homology and most preferably at least about 70% homology with the sequence shown in FIG. 5 (SEQ ID NO: 1) (Can fI) or FIG. 18 (SEQ ID NO: 67) (Can fII). Nucleic acids which encode peptides having a Can fI or Can fII activity and having at least about 90%, more preferably at least about 95%, and most preferably at least about 98–99% homology with a sequence set forth in FIG. 5 (SEQ ID NO: 2) (Can fI) or FIG. 18 (SEQ ID NO: 68) (Can fII) are also within the scope of the invention. Homology refers to sequence similarity between two peptides having an activity of Can fI or Can fII or between two nucleic acid molecules. Homology can be determined by comparing a position in each sequence which may be aligned for purposes of comparison. When a position in the compared sequence is occupied by the same base or amino acid, then the molecules are homologous at that position. A degree of homology between sequences is a function of the number of matching or homologous positions shared by the sequences.

Another aspect of the invention provides a nucleic acid which hybridizes under high or low stringency conditions to a nucleic acid which encodes a peptide having all or a portion of an amino acid sequence shown in FIG. 5 (SEQ ID NO: 2) (Can fI) or FIG. 18 (SEQ ID NO: 68) (Can fII). Appropriate stringency conditions which promote DNA hybridization, for example, 6.0× sodium chloride/sodium citrate (SSC) at about 45° C., followed by a wash of 2.0×SSC at 50° are known to those skilled in the art or can be found in Current Protocols in Molecular Biology, John Wiley & Sons, N.Y. (1989), 6.3.1–6.3.6. For example, the salt concentration in the wash step can be selected from a low stringency of about 2.0×SSC at 50° C. to a high stringency of about 0.2×SSC at 50° C. In addition, the temperature in the wash step can be increased from low stringency conditions at room temperature, about 22° C., to high stringency conditions at about 65° C.

Isolated nucleic acids encoding peptides having an activity of Can fI or Can fII, as described herein, and having a sequence which differs from the nucleotide sequences shown in FIG. 5 (SEQ ID NO: 1) and FIG. 18 (SEQ ID NO: 67) due to degeneracy in the genetic code are also within the scope of the invention. Such nucleic acids encode functionally equivalent peptides (i.e., a peptide having an activity of Can fI or Can fII) but differ in sequence from the sequences of FIG. 5 and FIG. 18 due to degeneracy in the genetic code. For example, a number of amino acids are designated by more than one triplet. Codons that specify the same amino acid, or synonyms (for example, CAU and CAC are synonyms for histidine) may result in “silent” mutations which do not affect the amino acid sequence of the Can fI or Can fII protein. However, it is expected that DNA sequence polymorphisms that do lead to changes in the amino acid sequence of Can fI or Can fII will exist within the dog dander population. One skilled in the art will appreciate that these variations in one or more nucleotides (up to about 3–4% of the nucleotides) of the nucleic acids encoding peptides having an activity of Can fI or Can fII may exist among individual pet dogs due to natural allelic variation. Any and all such nucleotide variations and resulting amino acid polymorphisms are within the scope of this invention. Furthermore, there may be one or more isoforms or related, cross-reacting family members of Can fI or Can fII. Such isoforms or family members are defined as proteins related in function and amino acid sequence to Can fI or Can fII, but encoded by genes at different loci.

Fragments of the nucleic acid encoding Can fI or Can fII are also within the scope of the invention. As used herein, a fragment of the nucleic acid encoding Can fI or Can fII refers to a nucleotide sequence having fewer nucleotides than the nucleotide sequence encoding the entire amino acid sequence of Can fI or Can fII protein and which encodes a peptide having an activity of Can fI or Can fII (i.e., a peptide having at least one biological activity of the Can fI or Can fII allergen) as defined herein.

Preferred nucleic acid fragments encode peptides of at least about 10 amino acid residues in length, preferably about 10–20 amino acid residues in length, and more preferably about 12–16 amino acid residues in length. Nucleic acid fragments which encode peptides having a Can fI activity of at least about 30 amino acid residues in length, at least about 40 amino acid residues in length, at least about 60 amino acid residues in length, at least about 80 amino acid residues in length, at least about 100 amino acid residues in length, and at least about 140 residues in length or more are also within the scope of this invention. Nucleic acid fragments which encode peptides having a Can fII activity of at least about 30 amino acid residues in length, at least about 40 amino acid residues in length, at least about 60 amino acid residues in length, at least about 80 amino acid residues in length, at least about 100 amino acid residues in length, at least about 140 residues in length, and at least about 160 amino acid residues in length or more are also within the scope of this invention.

Nucleic acid fragments within the scope of the invention include those capable of hybridizing under high or low stringency conditions with nucleic acids from other animal species for use in screening protocols to detect Can fI or Can fII or allergens that are cross-reactive with Can fI or Can fII. Generally, the nucleic acid encoding a peptide having an activity of Can fI or Can fII will be selected from the bases encoding the mature protein, however, in some instances it may be desirable to select all or part of a peptide from the leader sequence portion of the nucleic acids of the invention. Nucleic acids within the scope of the invention may also contain linker sequences, modified restriction endonuclease sites and other sequences useful for molecular cloning, expression or purification of recombinant peptides having an activity of Can fI or Can fII.

A nucleic acid encoding a peptide having an activity of Can fI or Can fII may be obtained from mRNA present in salivary glands or other organs of the pet dog Canis familiaris. It should also be possible to obtain nucleic acids encoding Can fI or Can fII from Canis familiaris genomic DNA. For example, the gene encoding Can fI or Can fII can be cloned from either a cDNA or a genomic library in accordance with protocols herein described. A cDNA encoding Can fI or Can fII can be obtained by isolating total mRNA from Canis familiaris. Double stranded cDNAs can then be prepared from the total mRNA. Subsequently, the cDNAs can be inserted into a suitable plasmid or bacteriophage vector using any one of a number of known techniques. Genes encoding Can fI or Can fII can also be cloned using established polymerase chain reaction techniques in accordance with the nucleotide sequence information provided by the invention. The nucleic acids of the invention can be DNA or RNA. A preferred nucleic acid is a cDNA encoding Can fI or Can fII having the sequence depicted in FIG. 5 (SEQ ID NO: 1) (Can fI) or FIG. 18 (SEQ ID NO: 67) (Can fII).

This invention also provides expression vectors containing a nucleic acid encoding a peptide having an activity of n I or Can fII, operably linked to at least one regulatory sequence. Operably linked is intended to mean that the nucleotide sequence is linked to a regulatory sequence in a manner which allows expression of the nucleotide sequence. Regulatory sequences are art-recognized and are selected to direct expression of the peptide having an activity of Can fI or Can fII. Accordingly, the term regulatory sequence includes promoters, enhancers and other expression control elements. Such regulatory sequences are described in Goeddel; Gene Expression Technology: Methods in Enzymology 185, Academic Press, San Diego, Calif. (1990). It should be understood that the design of the expression vector may depend on such factors as the choice of the host cell to be transformed and/or the type of protein desired to be expressed. In one embodiment, the expression vector includes a DNA encoding a peptide having an activity of Can fI or Can fII. Such expression vectors can be used to transfect cells to thereby produce proteins or peptides, including fusion proteins or peptides encoded by nucleic acids as described herein.

This invention further pertains to a host cell transfected to express a peptide having an activity of Can fI or Can fII. The host cell may be any procaryotic or eucaryotic cell. For example, a peptide having an activity of Can fI or Can fII may be expressed in bacterial cells such as E. coli, insect cells (baculovirus), yeast, or mammalian cells such as Chinese hamster ovary cells (CHO). Other suitable host cells can be found in Goeddel, (1990) supra or known to those skilled in the art.

Expression in eucaryotic cells such as mammalian, yeast, or insect cells can lead to partial or complete glycosylation and/or formation of relevant inter- or intra-chain disulfide bonds of recombinant protein. Examples of vectors for expression in yeast S. cerivisae include pYepSec1 (Baldari. et al., (1987) Embo J., 6: 229–234), pMFa (Kurjan and Herskowitz, (1982) Cell, 30: 933–943), pJRY88 (Schultz et al., (1987) Gene, 54: 113–123), and pYES2 (Invitrogen Corporation, San Diego, Calif.). Baculovirus vectors available for expression of proteins in cultured insect cells (SF 9 cells) include the pAc series (Smith et al., (1983) Mol. Cell Biol., 3: 2156–2165) and the pVL series (Lucklow, V. A., and Summers, M. D., (1989) Virology, 170: 31–39). Generally COS cells (Gluzman, Y., (1981) Cell, 23: 175–182) are used in conjunction with such vectors as pCDM 8 (Aruffo, A. and Seed, B., (1987) Proc. Natl. Acad. Sci. USA, 84: 8573–8577) for transient amplification/expression in mammalian cells, while CHO (dhfr-Chinese Hamster Ovary) cells are used with vectors such as pMT2PC (Kaufman et al., (1987) EMBO J., 6: 187–195) for stable amplification/expression in mammalian cells. Vector DNA can be introduced into mammalian cells via conventional techniques such as calcium phosphate or calcium chloride co-precipitation, DEAE-dextran-mediated transfection, or electroporation. Suitable methods for transforming host cells can be found in Sambrook et al., (Molecular Cloning: A Laboratory Manual, 2nd Edition, Cold Spring Harbor Laboratory press (1989)), and other laboratory textbooks.

Expression in procaryotes is most often carried out in E. coli with either fusion or non-fusion inducible expression vectors. Fusion vectors usually add a number of NH2 terminal amino acids to the expressed target gene. These NH2 terminal amino acids often are referred to as a reporter group. Such reporter groups usually serve two purposes: 1) to increase the solubility of the target recombinant protein; and 2) to aid in the purification of the target recombinant protein by acting as a ligand in affinity purification. Often, in fusion expression vectors, a proteolytic cleavage site is introduced at the junction of the reporter group and the target recombinant protein to enable separation of the target recombinant protein from the reporter group subsequent to purification of the fusion protein. Such enzymes, and their cognate recognition sequences, include Factor Xa, thrombin and enterokinase. Typical fusion expression vectors include pGEX (Amrad Corp., Melbourne, Australia), pMAL (New England Biolabs, Beverly, Mass.) and pRIT5 (Pharmacia, Piscataway, N.J.) which fuse glutathione S-transferase, maltose E binding protein, or protein A, respectively, to the target recombinant protein.

Inducible non-fusion expression vectors include pTrc (Amann et al., (1988) Gene, 69: 301–315) and pET 11d (Studier et al., Gene Expression Technology: Methods in Enzymology, 185, Academic Press, San Diego, Calif. (1990) 60–89). While target gene expression relies on host RNA polymerase transcription from the hybrid trp-lac fusion promoter in pTrc, expression of target genes inserted into pET 11d relies on transcription from the T7 gn10-lac 0 fusion promoter mediated by coexpressed viral RNA polymerase (T7 gn1). This viral polymerase is supplied by host strains BL21(DE3) or HMS174(DE3) from a resident λ prophage harboring a T7 gn1 under the transcriptional control of the lacUV 5 promoter.

One strategy to maximize recombinant Can fI or Can fII expression in E. coli is to express the protein in a host bacteria with an impaired capacity to proteolytically cleave the recombinant protein (Gottesman, S., Gene Expression Technology: Methods in Enzymology, 185, Academic Press, San Diego, Calif. (1990) 119–128). Another strategy would be to alter the nucleic acid encoding the Can fI or Can fII protein to be inserted into an expression vector so that the individual codons for each amino acid would be those preferentially utilized in highly expressed E. coli proteins (Wada et al., (1992) Nuc. Acids Res., 20: 2111–2118). Such alteration of nucleic acids of the invention can be carried out by standard DNA synthesis techniques.

The nucleic acids of the invention can also be chemically synthesized using standard techniques. Various methods of chemically synthesizing polydeoxynucleotides are known, including solid-phase synthesis which, like peptide synthesis, has been fully automated in commercially available DNA synthesizers (See e.g., Itakura et al., U.S. Pat. No. 4,598,049; Caruthers et al., U.S. Pat. No. 4,458,066; and Itakura, U.S. Pat. Nos. 4,401,796 and 4,373,071, incorporated by reference herein).

The present invention further pertains to methods of producing peptides that have an activity of Can fI or Can fII. For example, a host cell transfected with a nucleic acid vector directing expression of a nucleotide sequence encoding a peptide having an activity of Can fI or Can fII can be cultured under appropriate conditions to allow expression of the peptide to occur. The peptide may be secreted and isolated from a mixture of cells and medium containing the peptide having an activity of Can fI or Can fII. Alternatively, the peptide may be retained cytoplasmically and the cells harvested, lysed and the protein isolated. A cell culture includes host cells, media and other byproducts. Suitable media for cell culture are well known in the art. The peptide having an activity of Can fI or Can fII can be isolated from cell culture medium, host cells, or both using techniques known in the art for purifying proteins including ion-exchange chromatography, gel filtration chromatography, ultrafiltration, electrophoresis, and immunoaffinity purification with antibodies specific for a peptide having an activity of Can fI or Can fII.

Another aspect of the invention pertains to isolated peptides having an activity of Can fI or Can fII. A peptide having an activity of Can fI or Can fII has at least one biological activity of the Can fI or Can fII allergen. For example, a peptide having an activity of Can fI or Can fII may have the ability to induce a response in Can fI or Can fII specific T cells such as stimulation (T cell proliferation or cytokine secretion) or to induce T cell non-responsiveness. In one embodiment, a peptide having an activity of Can fI or Can fII stimulates T cells as evidenced by, for example, T cell proliferation or cytokine secretion. In another embodiment, peptides having a Can fI or Can fII activity induce T cell non-responsiveness in which T cells are unresponsive to a subsequent challenge with a Can fI or Can fII peptide following exposure to the peptide. In yet another embodiment, a peptide having a Can fI or Can fII activity has reduced IgE binding activity compared to purified, native Can fI or Can fII protein. A peptide having an activity of Can fI or Can fII may differ in amino acid sequence from the Can fI or Can fII sequence depicted in FIG. 5 (SEQ ID NO:2) (Can fI) or FIG. 18 (SEQ ID NO: 68) (Can fII) but such differences result in a modified protein which functions in the same or similar manner as a native Can fI or Can fII protein or which has the same or similar characteristics of a native Can fI or Can fII protein. Various modifications of the Can fI or Can fII protein to produce these and other functionally equivalent peptides are described in detail herein. The term peptide, as used herein, refers to peptides, proteins, and polypeptides.

A peptide can be produced by modification of the amino acid sequence of the Can fI or Can fII protein shown in FIG. 5 (SEQ ID NO: 2) (Can fI) or FIG. 18 (SEQ ID NO: 68) (Can fII), such as a substitution, addition, or deletion of an amino acid residue which is not directly involved in the function of the protein. Peptides of the invention can be at least about 10 amino acid residues in length, preferably about 10–20 amino acid residues in length, and more preferably about 10–16 amino acid residues in length. Peptides having an activity of Can fI or Can fII and which are at least about 30 amino acid residues in length, at least about 40 amino acid residues in length, at least about 60 amino acid residues in length, at least about 80 amino acid residues in length, and at least about 100 amino acid residues in length are also included within the scope of this invention.

Another embodiment of the invention provides a substantially pure preparation of a peptide having an activity of Can fI or Can fII. Such a preparation is substantially free of proteins and peptides with which the peptide naturally occurs (i.e., other canine peptides), either in a cell or when secreted by a cell.

The term isolated as used herein refers to a nucleic acid or peptide that is substantially free of cellular material or culture medium when produced by recombinant DNA techniques, or chemical precursors or other chemicals when chemically synthesized. Such proteins or peptides are also characterized as being free of all other dog dander proteins. Accordingly, an isolated peptide having an activity of Can fI or Can fII is produced recombinantly or synthetically and is substantially free of cellular material and culture medium or substantially free of chemical precursors or other chemicals and is substantially free of all other dog proteins. An isolated nucleic acid is also free of sequences which naturally flank the nucleic acid (i.e., sequences located at the 5′ and 3′ ends of the nucleic acid) in the organism from which the nucleic acid is derived.

Peptides having an activity of Can fI or Can fII can be obtained, for example, by screening peptides recombinantly produced from the corresponding fragment of the nucleic acid of Can fI or Can fII encoding such peptides. In addition, fragments can be chemically synthesized using techniques known in the art such as conventional Merrifield solid phase f-Moc or t-Boc chemistry. For example, the Can fI or Can fII protein may be arbitrarily divided into fragments of desired length with no overlap of the fragments, or preferably divided into overlapping fragments of a desired length. The fragments can be produced (recombinantly or by chemical synthesis) and tested to identify those peptides having a Can fI or Can fII activity (i.e., the ability to induce a T cell response such as stimulation (proliferation, cytokine secretion), nonresponsiveness, and/or has reduced IgE binding activity).

In one embodiment, peptides having an activity of Can fI or Can fII can be identified by the ability of the peptide to stimulate T cells or to induce T cell non-responsiveness. Peptides which stimulate T cells, as determined by, for example, T cell proliferation or cytokine secretion are defined herein as comprising at least one T cell epitope. T cell epitopes are believed to be involved in initiation and perpetuation of the immune response to the protein allergen which is responsible for the clinical symptoms of allergy. These T cell epitopes are thought to trigger early events at the level of the T helper cell by binding to an appropriate HLA molecule on the surface of an antigen presenting cell, thereby stimulating the T cell subpopulation with the relevant T cell receptor for the epitope. These events lead to T cell proliferation, lymphokine secretion, local inflammatory reactions, recruitment of additional immune cells to the site of antigen/T cell interaction, and activation of the B cell cascade, leading to the production of antibodies. One isotype of these antibodies, IgE, is fundamentally important to the development of allergic symptoms and its production is influenced early in the cascade of events at the level of the T helper cell, by the nature of the lymphokines secreted. A T cell epitope is the basic element, or smallest unit of recognition by a T cell receptor, where the epitope comprises amino acids essential to receptor recognition. Amino acid sequences which mimic those of the T cell epitopes and which modify the allergic response to protein allergens are within the scope of this invention.

Screening peptides for those which retain a Can fI or Can fII activity as described herein can be accomplished using one or more of several different assays. For example, in vitro, Can fI or Can fII T cell stimulatory activity is assayed by contacting a peptide known or suspected of having a Can fI or Can fII activity with an antigen presenting cell which presents appropriate MHC molecules in a T cell culture. Presentation of a peptide having a Can fI or Can fII activity in association with appropriate MHC molecules to T cells in conjunction with the necessary costimulation has the effect of transmitting a signal to the T cell that induces the production of increased levels of cytokines, particularly of interleukin-2 and interleukin-4. The culture supernatant can be obtained and assayed for interleukin-2 or other known cytokines. For example, any one of several conventional assays for interleukin-2 can be employed, such as the assay described in Proc. Natl. Acad. Sci USA, 86: 1333 (1989) the pertinent portions of which are incorporated herein by reference. A kit for an assay for the production of interferon is also available from Genzyme Corporation (Cambridge, Mass.).

Alternatively, a common assay for T cell proliferation entails measuring tritiated thymidine incorporation. The proliferation of T cells can be measured in vitro by determining the amount of ³H-labeled thymidine incorporated into the replicating DNA of cultured cells. Therefore, the rate of DNA synthesis and, in turn, the rate of cell division can be quantified.

In one embodiment, peptides which have Can fI or Can fII T cell stimulating activity (i.e., the peptide comprises at least one T cell epitope) can be identified using an algorithm which predicts the presence of T cell epitopes in a protein sequence, such as the algorithm described by Hill et al., Journal of Immunology, 147:189–197 (1991). The algorithm of Hill et al. predicts the location of T cell epitopes in a protein by the presence of certain patterns within the sequence which are likely to bind MHC and therefore may contain T cell epitopes. Based on the Hill et al. algorithm, two 13 amino acid peptides (discussed in Example 10) have been identified and produced synthetically. Such peptides were tested for T cell activity as described above (e.g., by measuring cellular uptake of tritiated thymidine). Specifically, in Example 10, human T cell stimulating activity was tested by culturing T cells obtained from an individual sensitive to Can fI (i.e., an individual who has an IgE mediated immune response to Can fI) with a peptide derived from Can fI and proliferation of T cells in response to the peptide was determined, e.g., by measuring cellular uptake of tritiated thymidine. Stimulation indices for responses by T cells to peptides were calculated as the maximum CPM in response to a peptide divided by the control CPM. A stimulation index (S.I.) equal to or greater than two times the background level was considered “positive”. Positive results were used to calculate the mean stimulation index for each peptide for the group of patients tested (See FIG. 25). Preferred peptides of this invention comprise at least one T cell epitope and have a mean T cell stimulation index of greater than or equal to 2.0. A peptide having a mean T cell stimulation index of greater than or equal to 2.0 in a significant number of dog dander allergen sensitive patients tested is considered useful as a therapeutic agent. Preferred peptides have a mean T cell stimulation index of at least 2.5, more preferably at least 3.0, more preferably at least 3.5, more preferably at least 4.0, more preferably at least 5.0 and most preferably at least about 6. For example, peptides having a Can fI activity and having a mean T cell stimulation index of at least 5, as indicated by data shown in FIG. 25, include Construct 1 (SEQ ID NO:105), Construct 2 (SEQ ID NO:106), and Construct 3 (SEQ ID NO:107). T cell epitopes can also be predicted and determined as described above for peptides derived from Can fII.

In addition, preferred peptides have a positivity index (P.I.) of at least about 60, more preferably about 100, more preferably at least about 200 and most preferably at least about 300. The positivity index for a peptide is determined by multiplying the mean T cell stimulation index by the percent of individuals, in a population of individuals sensitive to dog dander allergens (e.g., preferably a population of at least 12 individuals, more preferably a population of at least 30 individuals or more), who have a T cell stimulation index to such peptide of at least 2.0. Thus, the positivity index represents both the strength of a T cell response to a peptide (S.I.) and the frequency of a T cell response to a peptide in a population of individuals sensitive to dog dander allergens. In FIG. 10, the bar represents the positivity index and the percent of individuals tested who have a T cell stimulation index of at least 2.0 to various peptides derived from Can fI. For example, as shown in FIG. 25, Peptide A0095 has a mean S.I. of 3.0 and 43% of positive responses in the group of individuals tested resulting in a positivity index of 129.

In order to determine precise T cell epitopes by, for example, fine mapping techniques, a peptide having Can fI or Can fII T cell stimulating activity and thus comprising at least one T cell epitope as determined by T cell biology techniques is modified by addition or deletion of amino acid residues at either the amino or carboxy terminus of the peptide and tested to determine a change in T cell reactivity to the modified peptide. Following this technique, peptides are selected and produced recombinantly or synthetically. Peptides are selected based on various factors, including the strength of the T cell response to the peptide (e.g., stimulation index), the frequency of the T cell response to the peptide in a population of individuals sensitive to dog dander allergens, and the potential cross-reactivity of the peptide with other dog dander allergens. The physical and chemical properties of these selected peptides (e.g., solubility, stability) are examined to determine whether the peptides are suitable for use in therapeutic compositions or whether the peptides require modification as described herein. The ability of the selected peptides or selected modified peptides to stimulate human T cells (e.g., induce proliferation, lymphokine secretion) is then determined as described herein.

In another embodiment, a peptide having a Can fI or Can fII activity is screened for the ability to induce T cell non-responsiveness. The ability of a peptide known to stimulate T cells (as determined by one or more of the above described assays), to inhibit or completely block the activity of purified native Can fI or Can fII or portion thereof and induce a state of non-responsiveness can be determined using subsequent attempts at stimulation of the T cells with antigen presenting cells that present native Can fI or Can fII or peptide having a Can fI or Can fII activity following exposure to the peptide, having a Can fI or Can fII activity. If the T cells are unresponsive to the subsequent activation attempts, as determined by interleukin-2 synthesis and/or T cell proliferation, a state of non-responsiveness has been induced. See, e.g., Gimmi et al., (1993) Proc. Natl. Acad. Sci USA, 90: 6586–6590; and Schwartz (1990) Science, 248: 1349–1356, for assay systems that can be used as the basis for an assay in accordance with the present invention.

In yet another embodiment, peptides having a Can fI or Can fII activity are identified by IgE binding activity. For therapeutic purposes, peptides of the invention preferably do not bind IgE specific for a dog dander allergen, or bind such IgE to a substantially lesser extent than the corresponding purified native dog dander allergen binds such IgE. Reduced IgE binding activity refers to IgE binding activity that is less than that of purified native Can fI or Can fII protein. If a peptide having a Can fI or Can fII activity is to be used as a diagnostic reagent, it is not necessary that the peptide have reduced IgE binding activity compared to the native Can fI or Can fII allergen. IgE binding activity of peptides can be determined by, for example, an enzyme-linked immunosorbent assay (ELISA) using, for example, sera obtained from a subject, (i.e., an allergic subject) that has been previously exposed to the native Can fI or Can fII allergen. Briefly, the peptide suspected of having a Can fI or Can fII activity is coated onto wells of a microtiter plate. After washing and blocking the wells, antibody solution consisting of the plasma of an allergic subject who has been exposed to a peptide suspected of having a Can fI or Can fII activity is incubated in the wells. The plasma is generally depleted of IgG before incubation. A labeled secondary antibody is added to the wells and incubated. The amount ofIgE binding is then quantified and compared to the amount ofIgE bound by a purified, native Can fI or Can fII protein. Alternatively, the IgE binding activity of a peptide can be determined by Western blot analysis. For example, a peptide suspected of having a Can fI or Can fII activity is run on a polyacrylamide gel using SDS-PAGE. The peptide is then transferred to nitrocellulose and subsequently incubated with sera from an allergic subject. After incubation with a labeled secondary antibody, the amount ofIgE bound is then determined and quantified.

Another assay which can be used to determine the IgE binding activity of a peptide is a competition ELISA assay. Briefly, an IgE antibody pool is generated by combining plasma from dog dander allergic subjects that have been shown by direct ELISA to have IgE reactive with native Can fI or Can fII. This pool is used in ELISA competition assays to compare IgE binding of native Can fI or Can fII and a peptide suspected of having a Can fI or Can fII activity. IgE binding for the native Can fI or Can fII protein and a peptide suspected of having a Can fI or Can fII activity is determined and quantified.

If a peptide having an activity of Can fI or Can fII binds IgE, and is to be used as a therapeutic agent, it is preferable that such binding does not result in the release of mediators (e.g., histamines) from mast cells or basophils. To determine whether a peptide which binds IgE results in the release of mediators, a histamine release assay can be performed using standard reagents and protocols obtained, for example, from Amac, Inc. (Westbrook, Me.). Briefly, a buffered solution of a peptide suspected of having a Can fI or Can fII activity is combined with an equal volume of whole heparinized blood from an allergic subject. After mixing and incubation, the cells are pelleted and the supernatants are processed and analyzed using a radioimmunoassay to determine the amount of histamine released.

Peptides having an activity of Can fI or Can fII which are to be used as therapeutic agents are preferably tested in mammalian models of dog dander atopy, such as the mouse model disclosed in Tamura et al., (1986) Microbiol. Immunol., 30: 883–896, or in U.S. Pat. No. 4,939,239, or in the primate model disclosed in Chiba et al., (1990) Int. Arch. Allergy Immunol., 93: 83–88. Initial screening for IgE binding to a peptide having an activity of Can fI or Can fII may be performed by scratch tests or intradermal skin tests on laboratory animals or human volunteers, or in vitro systems such as RAST, RAST inhibition, ELISA assay, RIA (radioimmunoassay), or a histamine release assay, as described above.

It is possible to modify the structure of a peptide having an activity of Can fI or Can fII for such purposes as increasing solubility, enhancing therapeutic or prophylactic efficacy, or stability (e.g., shelf life ex vivo and resistance to proteolytic degradation in vivo). Such modified peptides are considered functional equivalents of peptides having an activity of Can fI or Can fII as defined herein. A modified peptide can be produced in which the amino acid sequence has been altered, such as by amino acid substitution, deletion, or addition, to modify immunogenicity and/or reduce allergenicity, or to which a component has been added for the same purpose.

For example, a peptide having an activity of Can fI or Can fII can be modified so that it maintains the ability to induce T cell non-responsiveness and bind MHC proteins without the ability to induce a strong proliferative response or possibly, any proliferative response when administered in immunogenic form. In this instance, critical binding residues for T cell receptor function can be determined using known techniques (e.g., substitution of each residue and determination of the presence or absence of T cell reactivity). Those residues shown to be essential to interact with the T cell receptor can be modified by replacing the essential amino acid with another, preferably similar amino acid residue (a conservative substitution) whose presence is shown to enhance, diminish but not eliminate, or not affect T cell reactivity. In addition, those amino acid residues which are not essential for T cell receptor interaction can be modified by being replaced by another amino acid whose incorporation may enhance, diminish but not eliminate, or not affect T cell reactivity, but does not eliminate binding to relevant MHC.

Additionally, a peptide having an activity of Can fI or Can fII can be modified by replacing an amino acid shown to be essential to interact with the MHC protein complex with another, preferably similar amino acid residue (conservative substitution) whose presence is shown to enhance, diminish but not eliminate, or not affect T cell activity. In addition, amino acid residues which are not essential for interaction with the MHC protein complex but which still bind the MHC protein complex can be modified by being replaced by another amino acid whose incorporation may enhance, not affect, or diminish but not eliminate T cell reactivity. Preferred amino acid substitutions for non-essential amino acids include, but are not limited to substitutions with alanine, glutamic acid, or a methyl amino acid.

Another example of modification of a peptide having an activity of Can fI or Can fII is substitution of cysteine residues preferably with alanine, serine, threonine, leucine or glutamic acid residues to minimize dimerization via disulfide linkages. In addition, amino acid side chains of fragments of the protein of the invention can be chemically modified. Another modification is cyclization of the peptide.

In order to enhance stability and/or reactivity, a peptide having an activity of Can fI or Can fII can be modified to incorporate one or more polymorphisms in the amino acid sequence of the protein allergen resulting from any natural allelic variation. Additionally, D-amino acids, non-natural amino acids, or non-amino acid analogs can be substituted or added to produce a modified protein within the scope of this invention. Furthermore, a peptide having an activity of Can fI or Can fII can be modified using polyethylene glycol (PEG) according to the method of A. Sehon and co-workers (Wie et al., supra) to produce a protein conjugated with PEG. In addition, PEG can be added during chemical synthesis of the protein. Other modifications of a peptide having an activity of Can fI or Can fII include reduction/alkylation (Tarr, Methods of Protein Microcharacterization, J. E. Silver ed., Humana Press, Clifton NJ 155–194 (1986)); acylation (Tarr, supra); chemical coupling to an appropriate carrier (Mishell and Shiigi, eds, Selected Methods in Cellular Immunology, WH Freeman, San Francisco, Calif. (1980), U.S. Pat. No. 4,939,239; or mild formalin treatment (Marsh, (1971) Int. Arch. of Allergy and Appl. Immunol., 41: 199–215).

To facilitate purification and potentially increase solubility of a peptide having an activity of Can fI or Can fII, it is possible to add an amino acid fusion moiety to the peptide backbone. For example, hexa-histidine can be added to the protein for purification by immobilized metal ion affinity chromatography (Hochuli, E. et al., (1988) Bio/Technology, 6: 1321–1325). In addition, to facilitate isolation of peptides free of irrelevant sequences, specific endoprotease cleavage sites can be introduced between the sequences of the fusion moiety and the peptide. In order to successfully desensitize a subject to Can fI or Can fII protein or related allergen, it may be necessary to increase the solubility of the protein by adding functional groups to the protein, or by omitting hydrophobic regions of the protein.

To potentially aid proper antigen processing of T cell epitopes within Can fI or Can fII, canonical protease sensitive sites can be engineered between regions, each comprising at least one T cell epitope via recombinant or synthetic methods. For example, charged amino acid pairs, such as KK or RR, can be introduced between regions within a protein or fragment during recombinant construction thereof. The resulting peptide can be rendered sensitive to cleavage by cathepsin and/or other trypsin-like enzymes which would generate portions of the protein containing one or more T cell epitopes. In addition, such charged amino acid residues can result in an increase in the solubility of the peptide.

Site-directed mutagenesis of a nucleic acid encoding a peptide having an activity of Can fI or Can fII can be used to modify the structure of the peptide by methods known in the art. Such methods may, among others, include polymerase chain reaction (PCR) with oligonucleotide primers bearing one or more mutations (Ho et al., (1989) Gene, 77: 51–59) or total synthesis of mutated genes (Hostomsky, Z. et al., (1989) Biochem. Biophys. Res. Comm, 161: 1056–1063). To enhance recombinant protein expression, the aforementioned methods can be applied to change the codons present in the cDNA sequence of the invention to those preferentially utilized by the host cell in which the recombinant protein is being expressed (Wada et al., supra).

Another aspect of the invention pertains to an antibody specifically reactive with a peptide having an activity of Can fI or Can fII. The antibodies of this invention can be used to standardize allergen extracts or to isolate the naturally-occurring or native form of Can fI or Can fII. For example, by using peptides having an activity of Can fI or Can fII based on the cDNA sequence of Can fI or Can fII, anti-protein/anti-peptide antisera or monoclonal antibodies can be made using standard methods. A mammal such as a mouse, a hamster or rabbit can be immunized with an immunogenic form of the peptide (e.g., Can fI or Can fII protein or an antigenic fragment which is capable of eliciting an antibody response). Techniques for conferring immunogenicity on a protein or peptide include conjugation to carriers or other techniques well known in the art. A peptide having an activity of Can fI or Can fII can be administered in the presence of adjuvant. The progress of immunization can be monitored by detection of antibody titers in plasma or serum. Standard ELISA or other immunoassay can be used with the immunogen as antigen to assess the levels of antibodies.

Following immunization, anti-Can fI or anti-Can fII antisera can be obtained and, if desired, polyclonal anti-Can fI or anti-Can fII antibodies isolated from the serum. To produce monoclonal antibodies, antibody producing cells (lymphocytes) can be harvested from an immunized animal and fused by standard somatic cell fusion procedures with immortalizing cells such as myeloma cells to yield hybridoma cells. Such techniques are well known in the art, for example the hybridoma technique originally developed by Kohler and Milstein, (1975) Nature, 256: 495–497) as well as other techniques such as the human B cell hybridoma technique (Kozbar et al., (1983) Immunology Today, 4: 72) and the EBV-hybridoma technique to produce human monoclonal antibodies (Cole et al., (1985) Monoclonal Antibodies and Cancer Therapy, Alan R. Liss, Inc. pp. 77–96). Hybridoma cells can be screened immunochemically for production of antibodies specifically reactive with a peptide having an activity of Can fI or Can fII and the monoclonal antibodies isolated.

The term antibody as used herein is intended to include fragments thereof which are also specifically reactive with the peptide having an activity of Can fI or Can fII. Antibodies can be fragmented using conventional techniques and the fragments screened for utility in the same manner as described above for whole antibodies. For example, F(ab′)₂ fragments can be generated by treating antibody with pepsin. The resulting F(ab′)₂ fragment can be treated to reduce disulfide bridges to produce Fab′ fragments. The antibody of the present invention is further intended to include bispecific and chimeric molecules having an anti-Can fI or anti-Can fII portion.

Another aspect of this invention provides T cell clones and soluble T cell receptors specifically reactive with a peptide having an activity of Can fI or Can fII. Monoclonal T cell populations (i.e., T cells genetically identical to one another and expressing identical T cell receptors) can be derived from an individual sensitive to Can fI or Can fII, followed by repetitive in vitro stimulation with a Can fI or Can fII protein or peptide having an activity of Can fI or Can fII in the presence of MHC-matched antigen-presenting cells. Single Can fI or Can fII MHC responsive cells can then be cloned by limiting dilution and permanent lines expanded and maintained by periodic in vitro restimulation. Alternatively, Can fI or Can fII specific T-T hybridomas can be produced by a technique similar to B cell hybridoma production. For example, a mammal, such as a mouse, is immunized with a peptide having an activity of Can fI or Can fII, T cells are then purified and fused with an autonomously growing T cell tumor line. From the resulting hybridomas, cells responding to a peptide having an activity of Can fI or Can fII are selected and cloned. Procedures from propagating monoclonal T cell populations are described in Cellular and Molecular Immunology (Abul K. Abbas et al. ed.), W.B. Saunders Company, Philadelphia, Pa. (1991) page 139. Soluble T cell receptors specifically reactive with a peptide having an activity of Can fI or Can fII can be obtained by immunoprecipitation using an antibody against the T cell receptor as described in Immunology: A Synthesis (Second Edition), Edward S. Golub et al., ed., Sinauer Associates, Inc., Sunderland, Mass. (1991) pages 366–269.

T cell clones specifically reactive with a peptide having an activity of Can fI or Can fII can be used to isolate and molecularly clone the gene encoding the relevant T cell receptor. In addition, a soluble T cell receptor specifically reactive with a peptide having an activity of Can fI or Can fII can be used to interfere with or inhibit antigen-dependent activation of the relevant T cell subpopulation, for example, by administration to an individual sensitive to Can fI or Can fII. Antibodies specifically reactive with such a T cell receptor can be produced according to the techniques described herein. Such antibodies can be used to block or interfere with the T cell interaction with peptides presented by MHC.

Exposure of allergic subjects to peptides having an activity of Can fI or Can fII and which have T cell stimulating activity, may cause the appropriate T cell subpopulations to become non-responsive to the respective protein allergen (e.g., fail to stimulate an immune response upon such exposure). In addition, such administration may modify the lymphokine secretion profile as compared with exposure to the naturally-occurring protein allergen or portion thereof (e.g., result in a decrease of IL-4 and/or an increase in IL-2). Furthermore, exposure to peptides having an activity of Can fI or Can fII which have T cell stimulating activity may influence T cell subpopulations which normally participate in the response to the allergen such that these T cells are drawn away from the site(s) of normal exposure to the allergen (e.g., nasal mucosa, skin, and lung) towards the site(s) of therapeutic administration of the protein or fragment derived therefrom. This redistribution of T cell subpopulations may ameliorate or reduce the ability of an individual's immune system to stimulate the usual immune response at the site of normal exposure to the allergen, resulting in a diminution in allergic symptoms.

A peptide having an activity of Can fI or Can fII when administered to a subject sensitive to dog dander allergens is capable of modifying the B cell response, T cell response, or both the B cell and the T cell response of the subject to the allergen. As used herein, modification of the allergic response of a subject to a dog dander allergen can be defined as non-responsiveness or diminution in symptoms to the allergen, as determined by standard clinical procedures (See e.g., Varney et al., (1990) British Medical Journal, 302: 265–269), including diminution in dog dander induced asthmatic symptoms. As referred to herein, a diminution in symptoms includes any reduction in the allergic response of a subject to the allergen following a treatment regimen with a peptide of the invention. This diminution in symptoms may be determined subjectively (e.g., the patient feels more comfortable upon exposure to the allergen), or clinically, such as with a standard skin test.

Peptides or antibodies of the present invention can also be used for detecting and diagnosing sensitivity to Can fI or Can fII. For example, this could be done by combining blood or blood products obtained from a subject to be assessed for sensitivity with peptide having an activity of Can fI or Can fII, under conditions appropriate for binding of components in the blood (e.g., antibodies, T cells, B cells) with the peptide(s) and determining the extent to which such binding occurs. Other diagnostic methods for allergic diseases which the peptides or antibodies of the present invention can be used include radio-allergosorbent test (RAST), paper radioimmunosorbent test (PRIST), enzyme linked immunosorbent assay (ELISA), radioimmunoassays (RIA), immuno-radiometric assays (IRMA), luminescence immunoassays (LIA), histamine release assays and IgE immunoblots.

The present invention further provides methods of detecting and treating sensitivity in a subject to Can fI or Can fII. The presence in subjects ofIgE specific for Can fI or Can fII and the ability of T cells of the subjects to respond to T cell epitopes of Can fI or Can fII can be determined by administering to the subject an Immediate Type Hypersensitivity test and/or a Delayed Type Hypersensitivity test (S e.g., Immunology (1985) Roitt, I. M., Brostoff, J., Male, D. K. (eds), C.V. Mosby Co., Gower Medical Publishing, London, N.Y., pp. 19.2–19.18; pp. 22.1–22.10) utilizing a peptide having an activity of Can fI or Can fII, or a modified form of a peptide having an activity of Can fI or Can fII, each of which binds IgE specific for the allergen. The same subjects are administered a Delayed Type Hypersensitivity test prior to, simultaneously with, or subsequent to administration of the Immediate Type Hypersensitivity test. Of course, if the Immediate Type Hypersensitivity test is administered prior to the Delayed Type Hypersensitivity test, the Delayed Type Hypersensitivity test would be given to those subjects exhibiting a specific Immediate Type Hypersensitivity reaction. The Delayed Type Hypersensitivity test utilizes a peptide having an activity of Can fI or Can fII which has human T cell stimulating activity and which does not bind IgE specific for the allergen in a substantial percentage of the population of subjects sensitive to the allergen (e.g., at least about 75%). Those subjects found to have both a specific Immediate type Hypersensitivity reaction and a specific Delayed Type Hypersensitivity reaction are administered an amount of a composition suitable for pharmaceutical administration. The composition comprises the peptide having an activity of Can fI or Can fII as used in the Delayed Type Hypersensitivity test and a pharmaceutically acceptable carrier or diluent.

A peptide having an activity of Can fI or Can fII can be used in methods of diagnosing, treating, and preventing allergic reactions to a dog dander allergen or a cross-reactive protein allergen. Thus, the present invention provides compositions suitable for pharmaceutical administration comprising an amount of at least one peptide having an activity of Can fI or Can fII and a pharmaceutically acceptable carrier. Administration of the compositions of the present invention to a subject to be desensitized can be carried out using known procedures, at dosages and for periods of time effective to reduce sensitivity (i.e., reduce the allergic response) of the subject to a dog dander allergen. The term subject is intended to include living organisms in which an immune response can be elicited, e.g., mammals. Examples of subjects include humans, dogs, cats, mice, rats, and transgenic species thereof. An amount of at least one peptide having an activity of Can fI or Can fII necessary to achieve a therapeutic effect may vary according to factors such as the degree of sensitivity of the subject to dog dander, the age, sex, and weight of the subject, and the ability of a peptide having an activity of Can fI or Can fII to elicit an antigenic response in the subject. Dosage regima may be adjusted to provide the optimum therapeutic response. For example, several divided doses may be administered daily or the dose may be proportionally reduced as indicated by the exigencies of the therapeutic situation.

The active compound (i.e., a peptide having an activity of Can fI or Can fII) may be administered in a convenient manner such as by injection (subcutaneous, intravenous, etc.), oral administration, inhalation, transdermal application, or rectal administration. Depending on the route of administration, the active compound may be coated in a material to protect the compound from the action of enzymes, acids and other natural conditions which may inactivate the compound.

To administer a peptide having an activity of Can fI or Can fII by other than parenteral administration, it may be necessary to coat the peptide with, or co-administer the peptide with, a material to prevent its inactivation. For example, a peptide having an activity of Can fI or Can fII may be administered to an individual in an appropriate carrier, diluent or adjuvant, co-administered with enzyme inhibitors or in an appropriate carrier such as liposomes. Pharmaceutically acceptable diluents include saline and aqueous buffer solutions. Adjuvant is used in its broadest sense and includes any immune stimulating compound such as interferon. Adjuvants contemplated herein include resorcinols, non-ionic surfactants such as polyoxyethylene oleyl ether and n-hexadecyl polyethylene ether. Enzyme inhibitors include pancreatic trypsin inhibitor, diisopropylfluorophosphate (DEP) and trasylol. Liposomes include water-in-oil-in-water CGF emulsions as well as conventional liposomes (Strejan et al., (1984) J. Neuroimmunol., 2: 27). For purposes of inducing T cell nonresponsiveness, the composition is preferably administered in non-immunogenic form, e.g., one that does not contain adjuvant.

The active compound may also be administered parenterally or intraperitoneally. Dispersions can also be prepared in glycerol, liquid polyethylene glycols, and mixtures thereof and in oils. Under ordinary conditions of storage and use, these preparations may contain a preservative to prevent the growth of microorganisms.

Pharmaceutical compositions suitable for injectable use include sterile aqueous solutions (where water soluble) or dispersions and sterile powders for the extemporaneous preparation of sterile injectable solutions or dispersion. In all cases, the composition must be sterile and must be fluid to the extent that easy syringability exists. It must be stable under the conditions of manufacture and storage and must be preserved against the contaminating action of microorganisms such as bacteria and fungi. The carrier can be a solvent or dispersion medium containing, for example, water, ethanol, polyol (for example, glycerol, propylene glycol, and liquid polyetheylene glycol, and the like), suitable mixtures thereof, and vegetable oils. The proper fluidity can be maintained, for example, by the use of a coating such as lecithin, by the maintenance of the required particle size in the case of dispersion and by the use of surfactants. Prevention of the action of microorganisms can be achieved by various antibacterial and antifungal agents, for example, parabens, chlorobutanol, phenol, ascorbic acid, thimerosal, and the like. In many cases, it will be preferable to include isotonic agents, for example, sugars, polyalcohols such as mannitol, sorbitol, sodium chloride in the composition. Prolonged absorption of the injectable compositions can be brought about by including in the composition an agent which delays absorption, for example, aluminum monostearate and gelatin.

Sterile injectable solutions can be prepared by incorporating active compound (i.e., a peptide having an activity of Can fI or Can fII) in the required amount in an appropriate solvent with one or a combination of ingredients enumerated above, as required, followed by filtered sterilization. Generally, dispersions are prepared by incorporating the active compound into a sterile vehicle which contains a basic dispersion medium and the required other ingredients from those enumerated above. In the case of sterile powders for the preparation of sterile injectable solutions, the preferred methods of preparation are vacuum drying and freeze-drying which yields a powder of the active ingredient (i.e., at least one peptide having an activity of Can fI or Can fII) plus any additional desired ingredient from a previously sterile-filtered solution thereof.

When the peptide having an activity of Can fI or Can fII is suitably protected, as described above, the peptide may be orally administered, for example, with an inert diluent or an assimilable edible carrier. The peptide and other ingredients may also be enclosed in a hard or soft shell gelatin capsule, compressed into tablets, or incorporated directly into the individual's diet. For oral therapeutic administration, the active compound may be incorporated with excipients and used in the form of ingestible tablets, buccal tablets, troches, capsules, elixirs, suspensions, syrups, wafers, and the like. The percentage of the compositions and preparations may, of course, be varied and may conveniently be between about 5 to about 80% of the weight of the unit. The amount of active compound in such therapeutically useful compositions is such that a suitable dosage will be obtained.

As used herein “pharmaceutically acceptable carrier” includes any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, and the like. The use of such media and agents for pharmaceutically active substances is well known in the art. Except insofar as any conventional media or agent is incompatible with the active compound, use thereof in the therapeutic compositions is contemplated. Supplementary active compounds can also be incorporated into the compositions.

It is especially advantageous to formulate parenteral compositions in dosage unit form for ease of administration and uniformity of dosage. Dosage unit form as used herein refers to physically discrete units suited as unitary dosages for the mammalian subjects to be treated; each unit containing a predetermined quantity of active compound calculated to produce the desired therapeutic effect in association with the required pharmaceutical carrier. The specification for the dosage unit forms of the invention are dictated by and directly dependent on (a) the unique characteristics of the active compound and the particular therapeutic effect to be achieved, and (b) the limitations inherent in the art of compounding such an active compound for the treatment of sensitivity in subjects.

The present invention also provides a composition comprising at least two peptides having an activity of Can fI or Can fII (e.g., a physical mixture of at least two peptides), each having T cell stimulating activity. For example, at least two peptides each having as activity of Can fI can be combined or at least two peptides each having an activity of Can fII can be combined, or at least one peptide having an activity of Can fI and at least one peptide having an activity of Can fII can be combined and administered. Alternatively, a peptide having at least two regions, each having T cell stimulating activity (i.e., each region comprising at least one T cell epitope) can be administered to an allergic subject. Such a peptide can have at least two regions derived from the same allergen, Can fI or Can fII, or a combination of Can fI and Can fII. A composition of two peptides or a peptide having at least two regions can be administered to a subject in the form of a composition with a pharmaceutically acceptable carrier as hereinbefore described. An amount of one or more of such compositions can be administered simultaneously or sequentially to a subject sensitive to a dog dander allergen to treat such sensitivity.

The cDNA (or the mRNA which served as a template during reverse transcription) encoding a peptide having an activity of Can fI or Can fII can be used to identify similar nucleic acid sequences in any variety or type of animal and, thus, to molecularly clone genes which have sufficient sequence homology to hybridize to the cDNA encoding a peptide having an activity of Can fI or Can fII. Thus, the present invention includes not only peptides having an activity of Can fI or Can fII, but also other proteins which may be allergens encoded by DNA which hybridizes to DNA of the present invention.

Isolated peptides that are immunologically related to Can fI or Can fII, such as by antibody cross-reactivity or T cell cross-reactivity, other than those already identified, are within the scope of the invention. Such peptides bind antibodies specific for the protein and peptides of the invention, or stimulate T cells specific for the protein and peptides of this invention.

A peptide having an activity of Can fI or Can fII (i.e., Can fI or Can fII produced recombinantly or by chemical synthesis) is free of all other dog dander proteins and, thus, is useful in the standardization of allergen extracts which are key reagents for the diagnosis and treatment of dog dander hypersensitivity. In addition, such a peptide is of a consistent, well-defined composition and biological activity for use in preparations which can be administered for therapeutic purposes (e.g., to modify the allergic response of a subject sensitive to dog dander). Such peptides can also be used to study the mechanism of immunotherapy of Canis familiaris allergy and to design modified derivatives or analogs useful in immunotherapy.

Work by others has shown that high doses of allergen extracts generally produce the best results during immunotherapy (i.e., best symptom relief). However, many subjects are unable to tolerate large doses of such extracts due to systemic reactions elicited by the allergens and other components within these preparations. A peptide having an activity of Can fI or Can fII of the invention has the advantage of being free of all other dander protein. Thus, such a peptide can be administered for therapeutic purposes.

It is now also possible to design an agent or a drug capable of blocking or inhibiting the ability of a dog dander allergen to induce an allergic reaction in sensitive subjects. Such agents could be designed, for example, in such a manner that they would bind to relevant anti-Can fI or anti-Can fII IgE molecules, thus preventing IgE-allergen binding, and subsequent mast cell/basophil degranulation. Alternatively, such agents could bind to cellular components of the immune system, resulting in suppression or desensitization of the allergic responses to dog dander allergens. A non-restrictive example of this is the use of peptides including B or T cell epitopes of Can fI or Can fII, or modifications thereof, based on the cDNA protein structure of Can fI or Can fII to suppress the allergic response to a dog dander allergen. This could be carried out by defining the structures of fragments encoding B and T cell epitopes which affect B and T cell function in vitro studies with blood components from subjects sensitive to dog dander.

The invention is further illustrated by the following examples which should not be construed as further limiting the subject invention. The contents of all references and published patent applications cited throughout this application are hereby incorporated by reference.

EXAMPLE 1 Protein Sequence Analysis of Purified Can fI

Affinity purified Can fI protein was obtained from Dr. Aalberse (de Groot, H. et al., supra). An Applied Biosystems Model 477A gas phase sequencer with on-line phynylthiohydantoin (HTH) amino acid analysis (Model 120A) was used to sequence the purified Can fI protein. A modification of the extraction program, multiple butylchloride extractions, was used to improve the amino acid recovery. O-phthaladehyde (OPA) was used in blocking of primary amines when proline was located at the amino terminus. Brauer, A. W., et al., (1984) Anal. Biochemistry, 137: 134, 142. In situ alkylation was performed by using the non-nucleophilic reductant, tributylphosphine with concomitant alkylation by 4-vinyl pyridine in ethylmorpholine buffer. Andrews, P. C. and Dixon, J. E., (1987) Anal. Biochemistry, 161: 524–528.

Using this methodology, the sequence of the N-terminus of the Can fI protein was determined, contrary to previous reports that the N-terminus is blocked (Schou, C. et al., supra). The N-terminal sequence of 65 amino acid residues which was identified through multiple N-terminal sequence analysis in conjunction with OPA blocking of contaminating signal represents a novel protein sequence (FIG. 5). The Can fI protein sequence was confirmed and expanded by sequence analysis of CNBr cleaved peptides. In situ CNBr digestion of Can fI on the sequence glass filter disk provided additional protein sequence information. Simpson, R. J. and Nice, E. C., (1984) Biochem. International, 8: 787–791. Prior to the in situ CNBr cleavage, forty-four cycles of amino acid sequencing were performed and then the protein sample was treated with OPA to block all amino groups. After five hours of in situ CNBr digestion, three major sequences were identified corresponding to the sequences after Met46, Met30 and an unknown Met, later shown to be Met103. An additional OPA block after cycle 18 (before Pro65) extended the sequence to Asp86. Sequence analysis of CNBr peptide fragments isolated by HPLC (Applied Biosystem, Inc., Model 130, C8 Column) further extended the N-terminal sequence to ninety-four amino acid residues. In situ CNBr cleavage in conjunction with OPA blocking also identified a 39 amino acid residue peptide (residues 104–142). A potential N-glycosylation site was found in the cDNA deduced amino acid sequence, Asn54-Ile55-Thr56. The protein sequence analysis identified the Ile55 and Thr56 of Can fI, however, nothing could be identified at the position 54. This suggests that post-translation modification occurs at Asn54 of Can fI and the modification is stable to the trifluoroacetic acid treatment during protein sequencing.

EXAMPLE 2 Extraction of mRNA From Canine Parotid Glands and Cloning of Can fI

A pair of fresh parotid glands from a single outbred dog were obtained from the Tufts University School of Veterinary Medicine (Worcester, Mass.) and, washed in phosphate buffered saline, and immediately frozen on dry ice. RNA was extracted essentially as described in the literature (Chirgwin, J. M. et al., (1979) Biochemistry, 18: 5294–5299.). One gland was pulverized to a powder with a mortar and pestle frozen in liquid N2, and suspended in 25 ml of GTC buffer (50% w/v guanidine thiocynate, 0.5% w/v Na lauryl sarcosine, 0.7% v/v β-mercaptoethanol, 0.1% v/v Sigma Antifoam A, 25 mM Na citrate, pH 7.0) and vortexed until dissolved. Genomic DNA present in the solution was sheared by forcing the solution through a 16 gauge needle until the viscosity of the solution no longer decreased. The sheared solution was centrifuged at 3 K rpm for 5 minutes at room temperature. The supernatant was then sheared further through a 23 gauge needle until its viscosity no longer decreased, and cleared by centrifugation at 5 K rpm for 5 minutes at room temperature. The solution was layered onto a CsCl cushion (5.7 M CsCl, 10 mM EDTA pH 7.5) and ultracentrifuged in a Beckman S W 41 Ti rotor at 35 K rpm for 16 hours at 20° C. The supernatant was discarded and the RNA pellet washed in 70% EtOH then resuspended in 0.3 M NaOAc, 10 mM EDTA, 0.1% SDS. Two volumes of absolute EtOH were added, and precipitation carried out on dry ice. RNA was pelleted by centrifugation, 70% EtOH washed, and resuspended in TES (10 mM Tris, 1 mM EDTA, 0.1% SDS). The final yield was ˜1.8 mg.

Single strand total dog parotid gland cDNA was synthesized using the above RNA preparation as a template in reverse transcription. 4 μg of total RNA were EtOH precipitated (using glycogen as carrier: molecular biology grade Boerhinger Manheim), 70% EtOH washed, and resuspended in 10 μl of dH₂O. Oligo dT(12-18) was added to 50 μg/ml and the RNA denatured at 70° C. for 5 minutes. The reaction was quick chilled on ice and 1 μl (40 units) of RNAsin (Promega) was added as a prophylactic against contaminating RNases. The components from the BRL Superscript™ Reverse Transcriptase Kit were added as follows: 4 μl 5× buffer, 2 μl 0.1 M DTT, 1 μl 10 mM dNTP mix. After warming the reaction to 37° C., 1 μl (200 units) of Superscript™ Reverse Transcriptase was added, and the reaction allowed to proceed for one hour at 37° C. Reverse transcription was terminated by incubation at 70° C. for 15 minutes, and the reaction stored at −20° C.

Initially the MOPAC (mixed oligonucleotides primed amplification of cDNA) technique of PCR amplification (Lee, C. C. et al., (1988) Science, 239: 1288–1291) was used to obtain a partial cDNA of Can fI encoding amino acids 14 to 29 of the mature protein. Using dog parotid cDNA as a template with degenerate primer pairs (synthesized on an Applied Biosystems 392) based on residues 9 to 15 (SEQ ID NO:3) [FIG. 1, S1A (SEQ ID NO:4) or SIB (SEQ ID NO:5)] and 30 to 37 (SEQ ID NO:10) [FIG. 1, AS2A (SEQ ID NO:11) or AS2B (SEQ ID NO:12)] of mature Can fI, a DNA fragment of the predicted size (˜3×28 amino acids, or 84 bp) could be amplified using a PCR kit (GeneAmp kit, Perkin Elmer Cetus, Norwalk, Conn.) in conjunction with the following program in an MJ Research Minicycler: 40× (92° C. 30 seconds/55° C. 1 minutes/75° C. 1 minutes). The primer pair 5′ S1B/3′ AS2B amplified the predicted fragment with the greatest efficiency, inferring that in both coding regions, the leucine residue was encoded by CTX rather than TT(A or G). As a test of its authenticity, the amplified fragment hybridized on a Southern blot to an internal degenerate oligonucleotide probe Dog probe 1 (SEQ ID NO:7), [based on Can fI residues 17 to 24, (SEQ ID NO:6)] that had been end labeled with γ-32P ATP using T4 polynucleotide kinase. After subcloning of the amplified fragment into Bluescript KS plasmid vector (Stratagene, San Diego, Calif.), it was sequenced using a Sanger dideoxy termination kit (USB Cleveland, Ohio) and shown to correctly encode residues 16 to 29 of mature Can fI.

Similarly, when amino acid sequence analysis of purified Can fI yielded sequence information extending to residue 94 of the mature protein, new primer pairs were used in MOPAC PCR amplification of an extended partial Can fI cDNA (residues 14 to 87). The 5′ or sense primers SA (residues 14 to 20) and SB (residues 21 to 27) were a nested pair based on the known Can fI partial cDNA sequence, while the 3′ or antisense primers, AS3A (SEQ ID NO:13) (FIG. 1) and AS3B (SEQ ID NO:14) (FIG. 1) were degenerate oligonucleotides based on residues 88 to 94. In sequential rounds of PCR ( 1/100th of the first reaction was used as template for the second reaction) using conditions described above in a pair of successive reactions using nested 5′ sense oligos in conjunction with a single 3′ antisense degenerate primer, a DNA fragment of the predicted size (˜3×80 amino acids, or 240 bp) could be amplified. Degenerate 3′ antisense oligo AS3B was more efficient in collaborating with the successive pairs of 5′ sense oligos to amplify the partial internal Can fI cDNA than oligo AS3A, again suggesting that the leucine residue was encoded by CTX rather than TT(A or G). The 240 bp DNA fragment was subcloned into Bluescript KS plasmid vector and sequenced as described above. It too proved to be an authentic Can fI cDNA. The missing residue in the amino acid sequence of Can fI at residue 54 was determined to be an asparagine on the grounds that: 1) no amino acid signal was found at residue 54 during protein sequence analysis; and 2) the asparagine residue resides within a consensus sequence for N-linked glycosylation (N54 I55 T56). These data strongly suggest that the N54 residue is modified by N-linked glycosylation.

To obtain the 3′ portion of the Can fI cDNA, the RACE (Rapid Amplification of cDNA ends) PCR protocol was employed (Frohman, M. A. et al., (1988) Proc. Natl. Acad. Sci., 85: 8998–9002). First strand cDNA synthesis from total dog parotid RNA was carried out as described above, except that the JM3 oligonucleotide was substituted for oligo dT as the primer in the reaction. The JM3 primer (SEQ ID NO:22) has an arbitrary tract of ˜40 nucleotides encoded 5′ of an oligo dT tract (FIG. 2). Hence, upon priming of poly A+ RNA to make cDNA, this known nucleotide tag is covalently linked to the 5′ end of the nascent cDNA transcripts. Using nested 5′ primers, SD (residues 73–79 (SEQ ID NO: 15)) and SE (residues 80–86 (SEQ ID NO: 17)), based on known Can fI cDNA sequence from MOPAC PCR analysis and nested primers based on the known JM3 primer sequence (JM3-1 (SEQ ID NO:23) and JM3-3 Bam (SEQ ID NO:24)) in PCR amplification as above (except the PCR program was 40×[92° C. 30 seconds/60° C. 1 minutes/75° C. 1 minutes]), a DNA fragment ˜500 bp in length was amplified. When probed against a kinase labeled degenerate oligonucleotide, Dog Probe 2 (SEQ ID NO:9) [residues 88 to 94 of mature Can fI (SEQ ID NO:8)], this band proved positive for hybridization. Upon subcloning into plasmid vector and DNA sequence analysis, three different partial 3′Can fI cDNAs were identified: Can fI (SEQ ID NO:61), 2Can fI (SEQ ID NO:62), and 3Can fI (SEQ ID NO:63), each as shown in FIG. 9. 2Can fI had a sequence that encoded a methionine residue followed by an asparagine-proline pair. These landmark residues for protein sequence analysis predicted: 1) a CNBr fragment with the NH2 terminal sequence MAKLLGRDPEQ . . . (SEQ ID NO:64); 2) an acid sensitive cleavage site at the DP pair; and 3) a proline residue which should prove refractory to OPA treatment and yield amino acid sequence data where all other NH2 termini would be blocked by the treatment. Indeed, further protein sequence analysis of purified Can fI did identify a CNBr fragment that in conjunction with OPA blockage at the internal proline residue had the sequence (M)AKLLGRDPEQSQEALEDF( )EFS( )AKGLNQEILELAQS(E)T (SEQ ID NO:65). Acid cleavage of the purified protein yielded a peptide with the sequence (D)PEQS(E)EA (SEQ ID NO:66). These complimentary data from protein sequence analysis and partial cDNA cloning of Can fI indicated that the authentic 3′ end of the Can fI cDNA may not have been isolated.

Comparison of the amino acid sequence data from sequencing purified Can fI and those encoded by the partial cDNAs 2Can fI and 3 Can fI inferred the origin of the multiple species of 3′ cDNAs may have been alternative splicing of the nascent Can fI transcript (note how in partial cDNA 3Can fI residues from the NH2 terminus of the CNBr fragment are found linked to the fragment's COOH terminal residues without the intervening residues). In contrast to this hypothesis of multiple cDNAs originating at the level of alternative splicing, the above PCR amplification of the 3′ end of the Can fI cDNA produced a single prominent DNA fragment ˜500 bp in length. However, the three partial 3′ cDNAs were either significantly longer or shorter than 500 bp. This suggested rare partial cDNAs were being subcloned, perhaps because the authentic Can fI cDNA harbored the restrictions site(s) encoded at the ends of the primers used in subcloning of DNA fragments that arise from PCR amplification. Hence, when digesting the PCR product representing the authentic Can fI cDNA with restriction endonucleases (in this case 5′ EcoRI and 3′ BamHI) one would 1) cut the authentic Can fI cDNA into at least two pieces, and 2) bias towards subcloning rare cDNAs that had arisen from alternative splicing of the nascent Can fI RNA transcripts that had exons containing EcoRI and/or BamHI sites deleted. To address this situation, new primers with different restriction enzyme sites at their 5′ ends were synthesized and used in RACE PCR of the 3′ end of the Can fI cDNA. The JM3-3 oligo was resynthesized with a BglII linked to its 5′ end [JM3-3XB (SEQ ID NO:21)] (FIG. 2), while the 5′ primers SD and SE were resynthesized with XhoI sites at their 5′ ends [XSD (SEQ ID NO: 16) and XSE (SEQ ID NO: 18)] (FIG. 2). After nested PCR of JM3 primed total dog parotid cDNA using these new primers and the previous amplification conditions, the intact 3′ end of the Can fI cDNA (which hybridized to kinase labeled Dog Probe 4, [(SEQ ID NO:20), residues 115–121 of mature Can fI (SEQ ID NO: 19) (FIG. 2)] was subcloned and sequenced. The translated amino acid sequence of the partial cDNA corresponded directly with the protein sequence data and extended it a further 6 amino acids before encountering a stop codon. As the cloning artifacts had predicted, both EcoRI and BamHI sites were found in the coding region of the intact 3′Can fI cDNA.

The 5′ end of the Can fI cDNA was cloned using an anchored PCR technique (Roux, K. H. and Dhanarajan, P., (1990) Biotechniques, 8: 48–57; Rafnar, T. et al., (1991) J. Biol. Chem., 266: 1229–1236). Double strand dog parotid cDNA was synthesized using a kit (BRL Superscript cDNA Synthesis System) employing the method of RNase H priming of the second strand of cDNA synthesis (Gubler, U., and Hoffman, B. J., (1983) Gene, 25: 263–269). The blunt double stranded cDNA was ligated to an anchor adapter, thereby placing a known sequence at the 5′ ends of cDNAs (SEQ ID NO:25; SEQ ID NO:26; and SEQ ID NO:27) (see FIG. 3). A primer based on the anchor sequence was used as a 5′ sense primer (AP) in conjunction with a nested pair of 3′ antisense primers, ASA (SEQ ID NO:31) [residues 18 to 24 (SEQ ID NO:30)] and ASB (SEQ ID NO:33) [residues 25 to 30 (SEQ ID NO:32)] based on known Can fI cDNA sequence from MOPAC PCR in sequential rounds of PCR (40×[92° C. 30 seconds/60° C. 1 minutes/75° C. 1 minutes]) to amplify the 5′ end of the Can fI cDNA (1° reaction ds anchored cDNA template with 5′ AP/3′ ASB primers: 2° reaction 1/100th 1° reaction template with 5′ AP/3′ ASA primers). Agarose gel electrophoresis analysis of the 2° reaction revealed a broad band ˜300 bp in length, which in Southern blot analysis hybridized to a 32P kinased degenerate oligonucleotide probe, Dog Probe 0 (SEQ ID NO:29) (FIG. 3), based on residues 9 to 17 (SEQ ID NO:28) of mature Can fI. The amplified fragment was subcloned into Bluescript KS plasmid and subjected to DNA sequence analysis. It's authenticity as the 5′ end of the Can fI cDNA was confirmed by the presence of the first 13 residues of mature Can fI protein at the 3′ end of the partial cDNA. Sequence of the longest partial 5′ cDNA extended a further 126 bp and encoded a 26 amino acid leader sequence not found in mature Can fI. Although no in-frame stop codons were found 5′ of the presumed initiator methionine codon (M-26), it is presumed to be the true initiator codon and not just an internal methionine residue because: 1) it is embedded within a consensus sequence for translation initiation in mammalian cells (Kozak, M., (1986) Cell, 44: 283–292); and 2) the predicted leader sequence is highly homologous to the leader sequences of proteins that are highly related to Can fI (see below).

A contiguous Can fI cDNA was then amplified and both strands directly sequenced as a PCR product to confirm the coding sequence of the molecule. To minimize the possibility of introducing errors in the amplified cDNA during the PCR reaction, PfuI DNA polymerase (Stratagene, San Diego, Calif.) was used to amplify the coding cDNA. PfuI DNA polymerase has been documented to introduce an order of magnitude fewer errors than Taq DNA polymerase during PCR (Lundberg, K. S., (1991) Gene, 108: 1–4). Direct sequencing of non-cloned DNA fragments from PCR reactions should also obviate any errors made by DNA polymerases during PCR since such errors will be scattered at random throughout the population of PCR products (Gyllensten, U. B., and Ehrlich, H. A., (1988) Proc. Natl. Acad. Sci. USA, 85: 7652–7656). Primers used in the amplification/sequencing included the 5′ sense leader ex oligo (SEQ ID NO:35) [residues −26 to −20 of Can fI (SEQ ID NO:34)] and the 3′ antisense stop BglII oligo (SEQ ID NO:36) [a 24-mer 40 bp 3′ of the stop codon of Can fI] (FIG. 4). A program of 40× (95° C. 30 seconds/60° C. 45 seconds/75° C. 45 seconds) was used with the aforementioned primers and PfuI DNA polymerase to amplify a DNA fragment ˜600 bp in length, which was subsequently isolated as a band on a 0.6% low melt agarose gel. This gel slice was melted at 70° C. and used as template for PCR sequencing using 32P labelled oligonucleotides as primers and a commercially available kit (AmpliTaq Cycle Sequencing Kit, Perkin Elmer Cetus, Norwalk, Conn.). A program of 30× (95° C. 30 seconds/60° or 68° C. 30 seconds) was used for the cycle sequencing. The PCR sequencing strategy to obtain unambiguous sequence of the mature Can fI protein from both strands of the amplified cDNA is depicted in FIG. 4 with the following sense primers: start ex (SEQ ID NO:37); SB (SEQ ID NO:38); SK (SEQ ID NO:39); SE (SEQ ID NO:40); and SH (SEQ ID NO:41), and the following antisense primers: Dog 9 (SEQ ID NO:42); ASK (SEQ ID NO:43); ASB (SEQ ID NO:44); and ASJ (SEQ ID NO:45). PCR cycle sequencing analysis of amplified cDNA encoding the mature Can fI protein served to confirm the DNA sequence obtained previously from cloned partial cDNAs of Can fI, FIG. 4.

In order to infer the possible biological function of Can fI, its amino acid sequence was compared to those in the GenBank, GenBankUpdate, EMBL, and EMBL Update sequence data bases (as of Jun. 25, 1992) using the NCBI BLAST network service (Altschul, S. F., et al., (1990) J. Mol. Biol., 215: 403–410). Can fI precursor protein (including the signal sequence not found in mature Can fI protein) displayed strong homology to three proteins: 1) Human von Ebner's gland protein; 2) Rat (VEG) von Ebner's gland protein precursor (Hartwig, S., et al., (1990) Nature, 343: 366–369); and 3) Rat odorant-binding protein (Pevsner, J., et al., (1988) Science, 241: 336–339). von Ebner's gland is a sublingual gland and secretes an abundant protein into the saliva speculated to be involved in potentiating the sense of taste involving hydrophobic molecules. von Ebner's gland protein belongs to a superfamily of lipophilic molecule carriers (Godovac-Zimmermann, J., (1988) Trends Biochem. Sci., 13: 64–66). The homology between Can fI and the human and rat von Ebner's gland proteins indicates that Can fI may be the canine homolog of von Ebner's gland protein. Additional data indicates that Can fI mRNA is expressed predominantly in the tongue epithelial tissue where von Ebner's glands are localized and only at a very low level (not detectable by Northern blot analysis) in parotid glands.

EXAMPLE 3 Protein Sequence Analysis of Purified Can fII

Affinity purified Can fII protein was obtained from Dr. Aalberse (de Groot, H. et al., supra). An Applied Biosystems Model 477A gas phase sequencer with on-line phynylthiohydantoin (HTH) amino acid analysis (Model 120A) was used to sequence the purified Can fII protein. A modification of the extraction program, multiple butylchloride extractions, was used to improve the amino acid recovery. O-phthaladehyde (OPA) was used in blocking of primary amines when proline was located at the amino terminus. Brauer, A. W., et al., (1984) Anal. Biochemistry, 137: 134, 142. In situ alkylation was performed by using the non-nucleophilic reductant, tributylphosphine with concomitant alkylation by 4-vinyl pyridine in ethylmorpholine buffer. Andrews, P. C. and Dixon, J. E., (1987) Anal. Biochemistry, 161: 524–528.

Using this methodology, the sequence of the N-terminus of the Can fII protein was determined. The N-terminal sequence of 38 amino acid residues which was identified through multiple N-terminal sequence analysis in conjunction with OPA blocking of contaminating signal represents a novel protein sequence FIG. 19 (SEQ ID NO: 88).

EXAMPLE 4 Extraction of mRNA from Canine Parotid Glands and Cloning of Can fII

The strategy used to clone Can fII is schematically drawn in FIG. 14. cDNA was synthesized using the above preparation as a template in reverse transcription. In the next step ds cDNA was used as a template for PCR along with degenerate primers which were designed based on amino acid sequence of Can fII and oriented to amplify a fragment of Can fII cDNA. PCR product was gel purified and than subjected to direct sequencing. The nucleotide sequence confirmed that the PCR product represents a fragment of Can fII cDNA. Further polymerase chain reactions were performed using Can fII specific primers in order to obtain a longer fragment which was subsequently used as a probe to screen a dog cDNA library. Positive clones were identified, plaque purified, sequenced and full length Can fII cDNA was obtained.

Fresh parotid glands from a single outbred dog were obtained from the Tufts University School of Veterinary Medicine (Worcester, Mass.), washed in phosphate buffered saline, and immediately frozen on dry ice. RNA was extracted essentially as described in the literature (Chirgwin, J. M. et al., (1979) Biochemistry, 18: 5294–5299.). Two glands (approx. 50 g) were pulverized to a powder with a mortar and pestle frozen in liquid N2, and suspended in 25 ml of GTC buffer (50% w/v guanidine thiocynate, 0.5% w/v Na lauryl sarcosine, 0.7% v/v b-mercaptoethanol, 0.1% v/v Sigma Antifoam A (Sigma, St. Louis Mo.), 25 mM Na citrate, pH 7.0) and vortexed until dissolved. Genomic DNA present in the solution was sheared by forcing the solution through a 16 gauge needle until the viscosity of the solution no longer decreased. The sheared solution was centrifuged at 3 K rpm for 5 minutes at room temperature. The supernatant was then sheared further through a 23 gauge needle until its viscosity no longer decreased, and cleared by centrifugation at 5 K rpm for 5 minutes at room temperature. The solution was layered onto a CsCl cushion (5.7 M CsCl, 10 mM EDTA pH 7.5) and centrifuged in a Beckman S W 41 Ti rotor at 35 K rpm for 16 hours at 17° C. The supernatant was discarded and the RNA pellet washed in 70% EtOH then resuspended in 0.3 M NaOAc, 10 mM EDTA, 0.1% SDS. Two volumes of absolute EtOH were added, and precipitation carried out on dry ice. RNA was pelleted by centrifugation, 70% EtOH washed, and resuspended in TES (10 mM Tris, 1 mM EDTA, 0.1% SDS). The final yield was ˜5.3 mg of total RNA. mRNA was isolated from total RNA by chromatography on oligo(dT) cellulose using the method described by Aviv, H. and Leder, P. (Proc. Natl. Acad. Sci. USA, (1972) 69: 1408). 20 μg of poly (A) RNA was obtained from 1.7 mg of total RNA.

The conversion of gland poly(A) mRNA into double stranded cDNA was carried out using standard procedure (Ausubel et al., (1993) Current Protocols in Molecular Biology, John Wiley & Sons). First, poly(A)RNA was copied onto cDNA was using Amersham cDNA Synthesis System Plus according to the manufacturer's procedure. 4 μg of poly (A) RNA was used as a template and oligo dT(12-18) was used to prime first strand synthesis. The RNA in RNA/DNA hybrid was than removed by RNaseH and the second strand was synthesized by DNA Polymerase I. Double stranded cDNA was completed and made blunt by T4 DNA polymerase and E. coli DNA ligase according to Gubler, U. and Hoffman, B. J., (1983) Gene, 25: 263).

Initially, PCR amplification (Mullis, K. B. and Faloona, F., (1987) Methods Enzymol, 155: 355–360) was used to obtain a partial cDNA of Can fII encoding amino acids 16 to 29 (SEQ ID NO: 97) of the mature protein. Using dog parotid cDNA as a template with degenerate primer pairs (synthesized on an Applied Biosystems 392) based on residues 3 to 6 (S1A) (FIG. 13) (SEQ ID NO: 91) and (S1B) (FIG. 13) (SEQ ID NO: 92) and on residues 33 to 38 (ASP2A) (FIG. 13) (SEQ. ID NO: 93) and (ASP2B) (FIG. 13) (SEQ ID NO: 94) of mature Can fII, a DNA fragment of the predicted size (˜120 bp) was amplified using a PCR kit (GeneAmp kit, Perkin Elmer Cetus, Norwalk, Conn.). Conditions for the reaction were: denaturation for 1 minute at 94° C.; annealing for 1 minute at 42° C. and polymerization for 1 minute at 72° C. The cycle was repeated 30 times. As a test of its authenticity, the amplified fragment was subjected to direct sequencing using a commercially available kit (AmpliTaq Cycle Sequencing Kit, Perkin Elmer Cetus, Norwalk, Conn.) according to the instructions supplied. Primers used in the amplification/sequencing (which included S1A, S1B, ASP2A and ASP2B) had been end labeled with γ-32P ATP using T4 polynucleotide kinase. The following program of 19 cycles (denaturation at 95° C. for 1 minute; annealing at 50° C. for 1 minute and extension at 72° C. for 15 seconds) was used for the cycle sequencing in a MJ Research Minicycler. The nucleotide sequence of about 40 nucleotides of the fragment was shown to correctly encode residues 16 to 29 of mature Can fII (SEQ ID NO: 97). The missing residue in the amino acid sequence of a native protein at the position 26 was found to be asparagine.

In order to generate a Can fII specific probe long enough (>100 bp) to be used to screen a cDNA library, the 5′ and 3′ ends of the Can fII cDNA were cloned using an anchored PCR technique (Roux, K. H. and Dhanarajan, P., (1990) Biotechniques, 8: 48–57; Rafnar., T. et al., (1991) J. Biol. Chem., 266: 1229–1236) (FIG. 15). Double stranded dog cDNA was synthesized as described above. The blunt double stranded cDNA was than ligated to an anchor adapter AT/AL (FIG. 16; SEQ ID NO: 96 and 102) thereby placing a known sequence at 5′ and 3′ ends of cDNAs (FIG. 15A). In order to obtain the 5′ end of Can fII cDNA, a primer based on the anchor sequence AP2 (FIG. 16) (SEQ ID NO: 95) was used as a 5′ primer in conjunction with 3′ antisense primers, D2-1 (residues 22 to 30) (FIGS. 13 and 16) (SEQ ID NO: 74), D2-2 (residues 17 to 25) (FIGS. 13 and 16) (SEQ ID NO: 75) and D2-3 (residues 16 to 21) (FIGS. 13 and 16) (SEQ ID NO: 76) based on known Can fII cDNA sequence obtained from initial PCR. Sequential rounds of PCR (40×[92° C. 30 seconds/60° C. 1 minute/75° C. 1 minute]) were carried out to amplify the 5′ end of the Can fII cDNA. In the 1° reaction, double stranded anchored cDNA was used as a template along with 5′ AP2/3′ D2-1 primers; in the 2° reaction 1/20th of the 1° reaction mixture was used with 5′ AP2/3′ D2-2 primers; in the 3° reaction 1/20th of 2° reaction mixture was used with AP2/D2–3 primers). 1% agarose gel electrophoresis of the reaction products revealed the presence of a single band of ˜300 bp long. As expected from the position of primers (see FIG. 15), the 2° and 3° reactions products migrated faster than 1° reaction product. The amplified fragment from the 3° reaction was gel purified and subjected to DNA sequence analysis. It's authenticity as the 5′ end of the Can fII cDNA was confirmed by the presence of the first N-terminal residues of mature Can fII protein (FIG. 15A, shaded residues). The 5′ portion of cDNA (FIG. 15A) (SEQ ID NO: 98) encoded part of the amino acid signal sequence which was not found in mature Can fII. The 3′ portion of Can fII (FIG. 15B) (SEQ ID NO: 99) was synthesized in an analogous manner as the 5′ end except that single stranded cDNA was used as a template and APA (FIG. 16) (SEQ ID NO: 100) was used as a 3′ primer and D2-4, (SEQ ID NO: 77), D2-5 (SEQ ID NO: 78) and D2-6 (SEQ ID NO: 79) (FIGS. 14 and 16) were used as internal primers in PCR. Direct sequencing of the PCR product from the 3° reaction revealed the presence of 8 amino acids of the known Can fII sequence followed by 8 amino acids downstream of the known sequence.

In order to clone the full length Can fII cDNA, a cDNA library was prepared and screened using standard published procedures (Gubler and Hoffman, Ausubel at al., supra). The lambda cDNA library was custom made by Clontech Laboratories, Inc. as follows: the first strand cDNA was primed from poly(A) RNA by oligo d(T)15. The blunt ended double stranded cDNA was ligated to an Eco RI linker CCGGAATTCCGG (SEQ ID NO: 101), digested with EcoRI, size selected in order to obtain fragments larger than 500 bp, and ligated into EcoRI cut and dephosphorylated vector λgt 10. The DNA was then packaged into lambda particles, plated on C600-hfl and C-600 E. Coli strains and the library titer was determined. The unamplified library consisted of 1.53×106 independent clones (clear plaques on C-600 hfl host) which contained inserts ranging in size from 0.6 kb to 3–4 kb. The average size of the insert as determined by PCR using Clontech λgt10 primers was 1.2 kb. 100,000 clones were plated on C-600hfl host and screened using Can fII specific probe. All manipulations leading to the cloning and sequencing of Can fII cDNA were done according to Protocols in Molecular Biology (Ausubel et al., supra). A Can fII probe was obtained by PCR amplification of dog cDNA using D2-9 (SEQ ID NO: 80) and D2-13 (SEQ ID NO: 83) primers (FIG. 16). The PCR product was then ³²P labeled by random priming. 20 positive clones were plaque purified, phage DNA was extracted from individual clones, digested with EcoRI and subcloned into pUC18. The presence of inserts was verified by digestion of the plasmid DNA with EcoRI and the nucleotide sequence of three individual clones was determined using Sequenase (United States Biochemicals) and AmpliTaq Cycle Sequencing kit (Perkin Elmer Cetus, Norwalk Conn.) according to manufacturer's instructions. PCR cycle sequencing analysis served to resolve some DNA sequence ambiguities resulting most probably from the formation of secondary structures on GC-rich Can fII template. The sequencing strategy is depicted in FIG. 17. Primers used in the sequencing/amplification included commercially available 16-mer Reverse Sequencing Primer (−21) and 17-mer Sequencing Primer (−20) from New England BioLabs as well as the Can fII specific primers listed in FIG. 16.

The nucleotide sequence of the three clones revealed the presence of an open reading frame which included 38 N-terminal amino acid residues (amino acids 1 to 38 on FIG. 13)(SEQ ID NO: 88) of mature Can fII identified earlier by protein sequencing and PCR sequencing of partial cDNA (see above). Sequencing strategy and features of three cDNA clones 1a, 1c and 1j are shown on the FIG. 17. Clone 1c of 791 bp (SEQ ID NO: 67) encodes the full length Can fII precursor protein (including signal sequence) and contains 5′ (bases 1 through 194) and 3′ (bases 738 trough 791) untranslated regions. Clones 1a of 793 bp (SEQ ID NO: 69) and 1j of 774 bp (SEQ ID NO: 71), encode precursor Can fII proteins in which part of the signal sequence is missing and contain 3′ untranslated regions which are longer then in 1c. The sequence alignment revealed a polymorphism among three clones (FIG. 18). The nucleotide sequence of 1a contains one nucleotide substitution (C to T at the position 607) and one deletion (at the position 752) compared to 1c (FIG. 18). The nucleotide sequence of 1j contains two nucleotide substitutions compared to 1a and 1c at positions 347 (T to C) and 401 (G to T). In addition, the sequence of clones 1a and 1c differ significantly at their 5′ and 3′ ends. The G to T substitution at the position 401 changes the predicted amino acid sequence of Can fII at residue 68 from glycine (GGC) to valine (GTC). All other nucleotide changes do not alter the amino acid sequence of Can fII since they are either silent mutations or they lie outside of the coding sequence of mature Can fII. The polymorphism among the cDNA clones may reflect the expression of Can fII genes from different alleles. It may also represent a cloning artifact due to the reverse trancriptase mediated synthesis of cDNA which may introduce errors (Holland et al., (1982) Science, 215: 1577–1585). For example, the purified HIV-1 reverse transcriptase was found to introduce misincorporations at a rate of 1/2000 to 1/4000 (Preston et al., (1988) Science, 242: 1168–1171). It is also possible that the formation of secondary structures on the GC-rich Can fII mRNA template may cause pausing of reverse transcriptase or abnormal termination of the synthesis.

The predicted sequence of Can fII protein shown in FIG. 18 (SEQ ID NO: 68) contains a 19 amino acid signal sequence encoded by base 195 through base 251 of the cDNA shown in FIG. 18 (SEQ ID NO: 67). This signal sequence is not found in the mature Can fII protein which is encoded by bases 252 through 734. The methionine codon at the position −19 is true initiator methionine codon and not just an internal methionine residue because: 1) the predicted amino acid sequence of a signal peptide (residues −19 to −1) is highly similar and identical in length to the signal sequences of proteins that are related to Can fII (see below); and 2) although another in-frame methionine codon is found 5′ of the presumed initiatior metionine (position −53) it is unlikely to be true because the deduced amino acid sequence of a peptide starting at the residue −53 is much longer than any known signal sequence and does not show any similarity to any known signal sequence. The Can fII cDNA encodes a protein having a predicted molecular weight of 18.2 kDa, with a single potential N-linked glycosylation site. Because 1) no amino acid signal was found at residue 25 during protein sequence analysis, and 2) the asparagine residue resides within a consensus sequence for N-linked glycosylation (N26 K27 S28), these data strongly suggest that the N26 residue is modified by N-linked glycosylation. N-linked glycosylation may increase the molecular weight of the mature protein. The deduced amino acid sequence of the mature protein encoded by the nucleic acid sequence is identical to the known NH2-terminal and internal amino acid sequence determined by amino acid sequence analysis of purified Can fII protein conducted as described in Example 3.

The expression of Can fII in various tissues was studied using the Northern blot technique. Poly (A) RNA or total RNA from various tissues was separated by electrophoresis through a 1.5% agarose gel containing 2.2 M formaldehyde. (Ausubel et al., supra). After electrophoresis, the separated RNAs were transferred onto GeneScreen membrane (NEN). Transfer, hybridization with a 32P labeled Can fII probe [obtained by PCR mediated amplification using D2-9 (SEQ ID NO: 14) and D2-13 (SEQ ID NO: 83) (FIG. 16) primers] and washings of the filter were performed according to the manufacturer's instructions. It appeared that the Can fII probe hybridized specifically at high stringency to RNA from dog parotid gland and to RNA from tongue epithelial tissue (FIG. 20). It did not hybridize to RNA from liver, or submaxiliary gland. Hybridization was observed to two bands of about 800 bp and 900 bp long, suggesting that Can fII may be encoded by two mRNA species. It is unlikely that two RNAs are transcribed from two different genes since a Southern blot experiment suggested that only a single copy Can fII geneis present in the dog genome. The two mRNAs encoding Can fII may be due to alternative splicing or to degradation of the mRNA. The former possibility seems very likely since different splicing configurations in the 3′ noncoding region has been described for proteins which are similar to Can fII (Clark et al., (1984) EMBO J., 3: 1045–1052, see also below).

In order to infer the possible biological function of Can fII, its amino acid sequence was compared to those in the GenBank, GenBankUpdate, EMBL, and EMBL Update sequence data bases using the NCBI BLAST network service (Altschul, S. F., et al., (1990) J. Mol. Biol., 215: 403–410). Can fII precursor protein displayed high similarity to two groups of related proteins: 1) Mouse Urinary Proteins (MUPs) (FIG. 21) (SEQ ID NO: 90) and 2) urinary a-2-globulins of rat (A2U) (FIG. 21) (SEQ ID NO: 89). The sequences of MUPs and A2Us show them both to be members of the lipocalin protein family (Cavaggioni et al., (1987) FEBS Lett., 212: 225–228). These are small proteins capable of binding hydrophobic molecules with high affinity and selectivity. This family now contains over 20 different proteins, principally identified through sequence homology (Flower et al., (1991) Biochim. Biophys. Res. Commun., 180: 69–74). The function of MUP and A2U remains unclear, but it is proposed that rodent urinary proteins are responsible for binding pheromones and their subsequent release from drying urine (Bocskei et al., (1992) Nature, 360: 186–188). They are synthesized at different levels in the liver and in the submaxillary, lachrymal, sublingual, parotid and mammary glands (Shahan et al., (1987) Mol. Cell. Biol., 7: 1947–1954). MUP IV for example, is expressed predominantly in the lachrymal and parotid glands, but not in liver (Shahan et al., supra). The amino acid similarity of Can fII, MUP and A2U as well as their pattern of expression may indicate that Can fII is canine homolog of lipocalins. Interestingly, immunologic and biochemical studies of MUPs and MUP-related proteins have shown that these proteins are important human allergens (Lorusso et al., (1986) J. Allergy Clin. Immunol., 78: 928; Platts-Mills et al., (1987) J. Allergy Clin. Immunol., 79: 505; Gurka et al., (1989) J. Allergy Clin. Immunol., 83: 945–954).

EXAMPLE 5 Bacterial Expression of Can fI

Bacterial expression of Can fI was performed as follows. The vector pET11d ΔHR His6 (Novagen, Madison, Wis.; modified at ImmuLogic Pharmaceutical Corporation by J. P. Morgenstern) was modified for expression of Can fI in E. coli, by removal of the internal EcoRI restriction site (at residues E143F144) from the Can fI cDNA to be inserted in the vector. This modification was necessary since all DNA fragments in this vector are cloned in frame with the His6 NH2 terminal leader sequence at a mutual 5′ EcoRI site. Hence, EcoRI sites internal to the insert must be avoided. The pET11d ΔHR His6 vector also requires that inserts have a 3′ BamHI site. However, since restriction sites such as BglII and Bcl I are compatible with BamHI overhangs, they could be placed at the 3′ end of the Can fI cDNA, avoiding the need to mutate the internal BamHI site. A cDNA encoding the mature Can fI protein had its internal EcoRI site removed, a unique EcoRI site placed at its 5′ end, and a BglII site placed at its 3′ end in a two step PCR reaction (Ho et al., supra) using PfuI DNA polymerase to minimize errors during amplification (FIG. 6). Two halves of the Can fI cDNA were amplified in primary PCR reactions (template: PCR fragment from cycle sequencing, program: 40×[95° 30 seconds/60° C. 45 seconds/75° C. 45 seconds]) with the 5′ portion of the molecule being amplified with the Start ex (SEQ ID NO:46 and SEQ ID NO:47)/EF antisense (SEQ ID NO:50 and SEQ ID NO:48) primer pair and the 3′ portion amplified with the sense EF (SEQ ID NO:49 and SEQ ID NO:48)/TAG BglII (SEQ ID NO:51 and SEQ ID NO:52) primer pair. Both EF primers were designed to introduce a point mutation in the EcoRI site at residues E143F144 of Can fI from GAATTC to GAGTTC, which would maintain the E143 residue since glutamate can be encoded by GAA or GAG codons.

Amplified DNA fragments of the expected size were isolated in gel slices from a 0.6% low melt agarose gel, melted at 70° C., mixed and used as template in a secondary (2°) PCR reaction with Start ex and TAG BglII primers. Mutagenized regions bearing the E143F144 pair should hybridize in the initial stages of the reaction to link the 5′ and 3′ ends of the Can fI cDNA, while the extreme 5′ and 3′ primers should serve to amplify the intact mutagenized cDNA. The entire reaction was phenol/chloroform extracted, EtOH precipitated, 70% EtOH washed, and digested with EcoRI and BglII. A band of the expected size (˜450 bp) was isolated as a gel slice from a 0.6% low melt agarose gel, melted at 70° C., ligated at room temperature to EcoRI/BamHI digested pET 11dΔHR His 6 plasmid, and the ligation transformed into XL-1 bacteria (Stratagene). Miniprep analysis of a 3 ml culture of one of the transformed colonies (using a Qiagen [Foster City, Calif.] plasmid mini kit) by Eco RV digestion revealed the presence of an insert of the appropriate size within the expression vector. A 300 ml culture seeded with this colony was grown, plasmid DNA extracted (Qiagen plasmid midi kit) and subjected to DNA sequence analysis. The entire 453 bp insert was shown to have the correct sequence for mature Can fI cDNA (including the mutated E143 codon from GAA to GAG), with the addition of an in-frame His6 reporter group (SEQ ID NO:53) encoded at its 5′ end. This His6 reporter group was to be used in metal ion affinity purification of the recombinant protein using NTA Ni++ chelating resin (Qiagen; Hochuli et al., supra).

A single colony of BL21(DE3) pET 11d ΔHR His6Can fIdRI bacteria was inoculated into a 2 ml brain heart infusion (BHI) culture (+200 μg/ml ampicillin) and incubated at 37° C. until turbid but not saturated. At this point 6 μl was removed and added to 600 μl of BHI and mixed. 100 μl was spread onto each of 6 BHI agar plates (+200 μg ampicillin) and incubated overnight at 37° C. The next morning the bacterial lawn was scraped off of the plates, pooled and resuspended in 20 ml of BHI media, and then aliquoted 1 ml each into each of 18 500 ml BHI cultures (+200 μg/ml ampicillin) in 2 liter Ehrlenmeyer flasks. Cultures were incubated at 37° and shaken at 300 rpm until the A600 reached 1.0. Isopropyl-β-D-thiogalactopyranoside (IPTG) was than added to final concentration of 1 mM to induce expression of the T7 RNA polymerase gene which would in turn induce expression of His6Can fI protein from the hybrid T7 gn10/lac 0 promoter. Expression was allowed to proceed for 2 hours after which the bacteria were pelleted and resuspended in 6 M guanidine hydrochloride (GuHCl), 100 mM NaPO4, 10 mM Tris, 100 mM 2-mercaptoethanol pH 8.0. Extraction was carried out for 1 hour with vigorous shaking and terminated by pelleting of the insoluble material at 10 K rpm in a JA-10 rotor (Beckman) for 1 hour. Supernatant was removed, and its pH adjusted to 8.0 before loading onto a 50 ml NTA agarose column that had been equilibrated in 6 M GuHCl, 100 mM NaPO4, 10 mM Tris, pH 8.0. The column was washed by step gradient as follows: 1) 6 M GuHCl, 100 mM NaPO4, 10 mM Tris, pH 8.0, 2) 8 M urea, 100 mM NaPO4, 10 mM Tris, pH 8.0, 3) 8 M urea, 100 mM NaOAc, 10 mM Tris, pH 6.3 with each wash proceeding until the A280 of the effluent from the column reached background. Recombinant His6Can fI protein was eluted from the column with 8 M urea, 100 mM NaOAc, 10 mM Tris, pH 4.5. Yield of the pooled peak fractions was ˜100 mg with a purity of ˜80% as determined by densitometry of a sample of the material analyzed by SDS-PAGE.

E. coli transformed with the vector pET11d containing the nucleic acid encoding Can fI have been deposited with the ATCC at accession number 69167.

EXAMPLE 6 Mammalian Expression of Can fI Protein

To produce a possibly glycosylated form of recombinant Can fI protein expressed in mammalian cells, Can fI expression was carried out as follows. Full length Can fI protein (including the leader sequence not found in the mature protein) when expressed in mammalian cells should be properly folded, glycosylated, and secreted. Two systems for high level transient expression of recombinant Can fI were employed. First, transient expression of recombinant Can fI with a His6 reporter group fused to its COOH terminus was performed in NIH 3T3 cells using the pJ7 Ω expression vector (Morgenstern, J. P. and Land, H., (1990) Nuc. Acids Res., 18: 1068). pJ7 Ω drives expression of genes inserted into its polylinker to high levels during transient transfection from its SCMV IE94 promoter (Morgenstern and Land, supra).

A cDNA encompassing the entire Can fI coding sequence was amplified using PfuI mediated PCR of total dog parotid cDNA with the 5′ Kozak leader (SEQ ID NO:54)/3′ TAG BglII (SEQ ID NO:51 and SEQ ID NO:52) primer pair (see FIG. 7). The entire PCR reaction was phenol-chloroform extracted, EtOH precipitated, 70% EtOH washed and digested with XhoI and BglII to generate correct overhangs for insertion into pJ7 Ω. A band of the expected size (˜600 bp) to encode the entire Can fI cDNA was isolated as a gel slice on a 0.6% low melt agarose gel, melted at 70° C. and ligated to Sal I/BglII digested pJ7 Ω at room temperature (see FIG. 7). The ligation was transformed into competent XL-1 Blue E. coli and positive colonies selected on ampicillin (200 μg/ml) dishes. DNA sequence analysis of the 5′ and 3′ ends of inserts was performed on plasmid obtained from 3 ml cultures of two colonies (using a Qiagen plasmid mini kit). Both plasmids had inserts with the correct sequence of the 5′ and 3′ ends of full length Can fI.

Next, to aid in purification of recombinant Can fI protein produced in mammalian cells (Jankecht, R., et al., (1991) Proc. Natl. Acad. Sci. USA, 88: 8972–8976), a His6 reporter group was to be fused at its COOH terminus. This was accomplished by excising the DNA fragment encoding the COOH terminus of Can fI as an EcoRI-BglII fragment and exchanging it with an EcoRI-BglII fragment encoding the COOH terminus of the protein that had been modified with the addition 6 histidines (FIG. 8). The COOH terminal His6 DNA fragment was generated by PCR of overlapping synthetic oligonucleotides as follows: a sense oligonucleotide (SEQ ID NO:56) encoding residues E123 to Q148 of the mature Can fI protein (SEQ ID NO:55.); Sense 3′ His6 link (SEQ ID NO:57); an antisense oligonucleotide encoding residues E141 to Q148/a His 6 tract/stop codon (SEQ ID NO:50 and SEQ ID NO:59); and 3′ His6 TAG BglII (SEQ ID NO:60), were synthesized and purified by OPC column chromatography (Applied Biosystems, Foster City, Calif.). In addition, smaller primers composed of the first 24 nucleotides of the aforementioned oligonucleotides, 5′ His6 link and 3′ His6 link, were also synthesized. Linking and amplifying the two long oligonucleotides to generate the EcoRI-BglII DNA fragment encoding the Can fI COOH terminus-His6 fusion was performed by PCR. 10 pmoles of each large oligonucleotide were used as substrate in PfuI mediated PCR with 1 μM primers using the program 40× (95° C. 30 seconds/60° C. 45 seconds/75° C. 30 seconds). The entire PCR reaction was phenol-chloroform extracted, EtOH precipitated, 70% EtOH washed and digested with EcoRI and BglII to generate correct overhangs for insertion into pJ7 Ω Can fI. A band of the expected size (˜110 bp) to encode the Can fI COOH terminus/His6 fusion was isolated as a gel slice on a 2.0% NuSieve agarose gel, melted at 70° C. and ligated to EcoRI/BglII digested pJ7 Ω Can fI at room temperature. The ligation was transformed into competent XL-1 Blue E. coli and positive colonies selected on ampicillin (200 μg/ml) dishes. Plasmid was isolated from 4 cultures inoculated with different colonies and subjected to DNA sequence analysis at the 3′ end of the insert. Clone #3 contained the expected His6 residues linked in frame to the COOH terminus of Can fI, so a large scale grow of this culture was undertaken to obtain large quantities of the pJ7 Ω Can fI His6 plasmid for transfection. A one liter culture was amplified in 15 μM chloramphenicol once A600 reached 0.6. 800 μg of plasmid were isolated after alkaline lysis and two successive rounds of CsCl banding (Sambrook et al., supra).

Ten plates of NIH 3T3 cells were seeded at a density of 1.7×106 cells per 15 cm tissue culture dish, and the following morning, subjected to calcium phosphate transfection with 20 μg/dish of pJ7 Ω Can fI His6 plasmid (Parker, B. A., and Stark, G. R., (1979) J. Virol., 31: 360–369). 48 hours post transfection, supernatant was pooled from the dishes, filtered through a 0.45μ unit (Costar), and brought to a concentration of 1 μM imidazole, with the addition of protease inhibitors 1 mM PMSF, 1 μg/ml, pepstatin 1 μg/ml soybean trypsin inhibitor, and 1 μg/ml leupeptin. Metal ion affinity purification of the Can fIHis6 protein was achieved by loading the supernatant onto a 2 ml NTA agarose (Qiagen) column that had been equilibrated in 1×PBS, 1 mM imidazole, 1 mM PMSF, 1 μg/ml pepstatin, 1 μg/ml soybean trypsin inhibitor, and 1 μg/ml leupeptin. Non-specifically bound proteins were washed off the column with 10 column volumes of 1×PBS, 20 mM imidazole, 1 mM PMSF, 1 μg/ml pepstatin, 1 μg/ml soybean trypsin inhibitor, and 1 μg/ml leupeptin. Can fI His6 protein was specifically eluted from the column in 1×PBS, 80 mM imidazole, 1 mM PMSF, 1 μg/ml pepstatin, 1 μg/ml soybean trypsin inhibitor, and 1 μg/ml leupeptin (Hoffmann, A. and Roeder, R. G., (1991) Nuc. Acids. Res., 19: 6337–6338, and Janknecht et al., supra). Aliquots of the eluted fractions were analyzed by 12% SDS PAGE. Coomasie blue staining of the gel revealed three major bands of molecular weight ˜70 kDa, 45 KDa, and 25 KDa. Since the molecular weight of native immunoaffinity purified Can fI is 25 KDa (Schou et al., supra and de Groot et al., supra) it was suspected that the smallest band on the SDS gel was recombinant Can fI His6.

EXAMPLE 7 Direct Binding of Human IgE to Recombinant Can fI by ELISA and Western blot

An ELISA plate (IMMULON II Dynatech, Chantilly, Va.) was coated with bacterially expressed recombinant Can fI, (rCan fI) at 0.5 μg/well in PBS-Tween and incubated overnight at 4° C. The coating antigen was removed and the wells were blocked with 0.5% gelatin in PBS, 200 μl/well for two hours at room temperature. Plasma from a skin test positive dog allergic patient, #901, was serially diluted with PBS-Tween and 100 μl was added per well and incubated overnight at 4° C. (the plasma dilutions were tested in duplicate). The second antibody (biotinylated goat anti-human IgE 1:1000, Kirkegaard & Perry Laboratories) was added at 100 μl/well for one hour at room temperature. This solution was removed and streptavidin-HRPO at 1:10,000, (Southern Biotecnology Associates, Inc. Birmingham, Ala.) was added for one hour at room temperature. TMB Membrane Peroxidase Substrate system (Kirkegaard & Perry Laboratories) was freshly mixed and added at 100 μl. The color was allowed to develop for 2–5 minutes. The reaction was stopped by the addition of 100 μl/well of 1M phosphoric acid. The plate was read on a Mircoplate EL 310 Autoreader (Biotek Instruments, Winooski, Vt.) with a 450 nm filter. The absorbance levels of duplicate wells were averaged. The graphed results are shown in FIG. 11. The data shows that patient #901 has a high level of anti-Can f specific IgE such that at 1/162 dilution (the highest plasma dilutin used) the binding level to the recombinant Can fI is still two-fold above background. A known negative patient (#250) was also tested and shown to be negative by this assay.

Western Blot analysis of four different protein preparations as potential sources Can fI was performed. The four different prepparations used for Western blotting were: dog hair extract, dog saliva, bacterially expressed rCan fI (used for the ELISA) and rCan fI as expressed in a mammalian cell culture system. These preparations were loaded on a 15% acrylamide SDS-PAGE (lanes 1–4, respectively) at 5 μg/lane. The protein concentrations were based on the Bicinchoninic acid (BCA) assay (Pierce, Rockford, Ill.). Following electrophoresis, the proteins were transferred to nitrocellulose and stained with India Ink. The nitrocellulose sections were blocked by incubation in Tween solution with 1% milk/1% BSA for 30 minutes room temperature, then probed with patient #901 plasma or negative control patient #250 at a 1:20 dilution in tween mild solution. This first antibody incubation was carried out overnight at room temperature. Biotinylated goat anti-human IgE (KPL) was used as the second antibody at a 1:5000 dilution for a two hour incubation. Streptavidin-HRPO (1:20,000 dilution) and the ECL Western Blot Detection system (Amersham, Arlington Heights, Ill.) were used for detection by chemiluminescence. A 20 second exposure was performed and the film developed. The results from this assay show no recognition of the protein preparations by patient #250 IgE. The IgE from dog allergic patient #901 shows distinct binding to Can fI proteins in the saliva and the bacterially expressed recombinant Can fI (lanes 2 and 3, FIG. 12). The sizes of the protein forms are different between the two preparations and this is due to fact that the native Can fI protein found in dog saliva is glycosylated and runs with an apparent molecular weight of 28,000 daltons whereas the recombinant form from bacteria has no carbohydrate modification. The binding of IgE from serum of patients #901 to the mammalian expressed rCan fI is extremely faint and at present is only suggestive of positive expression. The full length bacterially produced form, lane 3, has an apparent molecular weight of 18,000 daltons and the larger IgE binding proteins in both lanes 2 and 3 are most likely dimeric structures of the lower molecular weight proteins.

EXAMPLE 8 Bacterial Expression of Can fII

In an attempt to readily produce large amounts of pure recombinant Can fII protein, expression of Can fII in bacteria was carried out as follows. Full length cDNA encoding mature Can fII protein was obtained by amplification of the molecule from total parotid cDNA in PCR using D2-3pet (SEQ ID NO: 103) and D2-Spet (SEQ ID NO: 104) primer pair (FIG. 13). Primers were designed to introduce EcoRI and BamHI restriction sites at 5′ and 3′ of cDNA molecule respectively. The pET11d ΔHR His6 vector requires that inserts have 5′ EcoRI site and 3′ BamHI site.

Amplified DNA fragment of the expected size was purified by electrophpresis in low melting agarose and ligated at room temperature to EcoRI/BamHI digested pET11d ΔHR His6 plasmid and the ligation mixture was used to transform XL-1 Blue bacteria (Stratagene). Miniprep analysis of several transformed colonies (using Qiagen [Foster City, Calif.] plasmid mini kit) revealed the presence of an insert of the appropriate size within the expression vector. A 300 ml culture inoculated with one colony was grown, plasmid DNA extracted and subjected to sequence analysis. The entire 486 bp insert was shown to have the correct sequence for the mature Can fII cDNA with the addition of a reporter group encoded at the 5′ end. This His6 reporter group was to be used in metal ion affinity purification of the recombinant protein using NTA Ni++ chelating resin (Qiagen). A single colony of BL21 (DE3) pET 11d ΔHR His6Can fII bacteria was inoculated into a 2 ml brain heart infusion (BHI) culture (+200 μg/ml ampicillin) and incubated at 37° C. until turbid but not saturated. At this point 6 μl was removed and added to 600 μl of BHI and mixed. 100 μl was spread onto each of 6 BHI agar plates (+200 μg ampicillin) and incubated overnight at 37° C. The next morning the bacterial lawn was scraped off of the plates, pooled and resuspended in 20 ml of BHI media, and then aliquoted 1 ml each into each of 18 500 ml BHI cultures (+200 μg/ml ampicillin) in 2 liter Ehrlenmeyer flasks. Cultures were incubated at 37° C. and shaken at 300 rpm until the A600 reached 1.0. Isopropyl-β-D-thiogalactopyranoside (IPTG) was than added to 1 mM to induce expression of the T7 RNA polymerase gene which would in turn induce expression of His6Can fII protein from the hybrid T7 gn10/lac O promoter.

Expression was allowed to proceed for 2 hours after which the bacteria were pelleted and resuspended in 6 M guanidine hydrochloride (GuHCl), 100 mM NaPO4, 10 mM Tris, 100 mM 2-mercaptoethanol pH 8.0. Extraction was carried out for 1 hour with vigorous shaking and terminated by pelleting of the insoluble material at 10 K rpm in a JA-10 rotor (Beckman) for 1 hour. Supernatant was removed, and its pH adjusted to 8.0 before loading onto a 50 ml NTA agarose column that had been equilibrated in 6 M GuHCl, 100 mM NaPO4, 10 mM Tris, pH 8.0. The column was washed by step gradient as follows: 1) 6 M GuHCl, 100 mM NaPO4, 10 mM Tris, pH 8.0, 2) 8 M urea, 100 mM NaPO4, 10 mM Tris, pH 8.0, 3) 8 M urea, 100 mM NaOAc, 10 mM Tris, pH 6.3 with each wash proceeding until the A280 of the effluent from the column reached background. Recombinant His6Can fII protein was eluted from the column with 8 M urea, 100 mM NaOAc, 10 mM Tris, pH 4.5. Yield of the pooled peak fractions was ˜100 mg with a purity of ˜80% as determined by densitometry of a sample of the material analyzed by SDS-PAGE.

E. coli transformed with the vector pET11d containing the nucleic acid encoding Can fII have been deposited with the ATCC at accession number XXXX.

EXAMPLE 9 Direct Binding of Human IgE to Native and Recombinant Can fII

Plasma samples from 14 dog-allergic patients (skin test 4+) were assayed for IgE binding to native Can fII and rCan fII. An ELISA plate (Immulon II Dynatech, Chantilly, Va.) was coated with native and bacterially expressed recombinant Can fII at 0.5 μg/well in PBS-Tween and incubated overnight at 4° C. The coating antigen was removed and the wells were blocked with 0.5% gelatin in PBS, 200 μl/well for two hours at room temperatre. Binding of human IgE to the coating antigen was detected using biotinylated goat-anti-human IgE, streptavidin linked to peroxidase and TMB substrate. Reactions were read on a plate reader at 450 nm (A450). Of 14 plasma samples tested for IgE to native Can fII, 5 contained detectable antibody binding (FIG. 22A), with plasma from patients #901 and #227 containg the highest levels. Similarly, of 23 plasma samples tested for IgE to recombinant, bacterially expressed Can fII, several contained detectable antibody binding (FIGS. 22B and C).

EXAMPLE 10 Can fI Human T Cell Proliferation Analysis

To identify peptides having Can fI T cell stimulating activity several peptides derived from Can fI were produced and cultured with human T cell lines primed with recombinant Can fI protein and the responses were determined by standard T cell proliferation assays. A set of peptides derived from Can fI (Construct 1 (SEQ ID NO: 105), Construct 2 (SEQ ID NO: 106), and Construct 3 (SEQ ID NO: 107)), each representing a portion of the Can fI protein were used in proliferation assays. In addition, the assays included two peptides (A0095 (SEQ ID NO: 108), amino acids 7 through 19; and A0096 (SEQ ID NO: 109); amino acids 42 through 54) which were selected as containing potential T cell epitopes using the algorithm described in Hill et al., Journal of Immunology 147: 184–197.

Constructs 1, 2 and 3 were produced by expressing and purifying portions of the Can fI protein in E. coli using standard techniques. DNA fragments encoding Construct 1 (amino acids 1 through 65 of Can fI) and Construct 2 (amino acids 56 through 108) were obtained by amplification from a plasmid pET11dΔ HRHis6Can fIΔ containing full length Can fI cDNA and were subcloned into an EcoRI/BamHI site of pET11d vector containing a His6 reporter sequence. A DNA fragment encoding Construct 3 (amino acids 90 through 148) was amplified from the same plasmid and subcloned into an EcoRI site of pET11d vector. Recombinant proteins were affinity purified on a NTA Ni⁺⁺ chelating resin (Qiagen) according to published protocol.

In order to perform in vitro assays of human T cell proliferative response to Can fI and the five Can fI peptides described above, whole blood obtained from subjects allergic to Can fI in a skin prick test was passed through a Lymphocyte Separation Media (LSM) to remove platelets, red blood cells and granulocytes. The resulting peripheral blood mononuclear cells (PBMC) were stimulated with 50 μg/ml of recombinant Can fI produced as described in Example 2 for 6 days in RPMI 1640 medium supplemented with 5% heat inactivated human AB serum, 2 mM L-glutamine, 10 mM HEPES, 50 μM 2-mercapto-ethanol and 100 U/ml penicillin and streptomycin.

A second separation LSM was performed to remove high density cell debris and dead cells. The resulting PBMC cells were allowed to proliferate for 12–18 days. During this time the medium was supplemented with additions of recombinant IL2 (Sunits/ml) and IL4 (Sunits/ml.).

When the lymphocytes reached a point of rest (determined such that an overnight pulse of 20,000 cells with ³H thymidine was within the 2000–4000 CPM range), the cells were restimulated for analysis in secondary proliferation assays. Secondary T cell proliferation assays included 2×10⁴ T cells/well, 5×10⁴ PBMC/well (irradiated with 3500 rads) as antigen presenting cells. Antigens were assayed in duplicate or triplicate wells at the following concentrations:

-   -   rCan fI: 4, 20 and 100 μg/ml.     -   Peptides: 3, 15, and 75 μg/ml.     -   Dog extract: 3, 15 and 75 μg of protein/ml. The concentration of         Can fI in this preparation dog extract is unknown.     -   Constructs: initially at a single concentration of 20 μg/ml,         then at 3, 15, and 75 μg/ml. Constructs were insoluble at 75         μg/ml.

PHA was added at 1 μg/ml to indicate nonspecific activation ability. Tetanus toxoid, an irrelevant antigen, was added at dilutions of 1:2000, 1:4000 and 1:8000 to indicate T cell specificity.

After 3 days of culture under conditions of secondary assay 1 μCi of ³H thymidine was added to each culture well for overnight incubation. Cultures were harvested on glass fiber filters and ³H thymidine incorporation was measured by β scintillation counting. Stimulation indices which measure the strength of a T cell response to a peptide were calculated by dividing ³H thymidine uptake of treated cultures by ³H thymidine uptake of untreated medium controls.

The results of the secondary T cell proliferation assays are shown in FIGS. 24–25. FIG. 24 graphically compares the stimulation indices of individual subjects to rCan fI, peptides A0095–A0096 and Constructs 1–3. This comparison indicates that significant areas of T cell reactivity in the Can fI protein are found at all three parts of the protein, as shown by the substantial stimulation indices of Constructs 1-3 which, together, encompass the entire Can fI protein sequence.

Positivity indices for the peptides shown in FIG. 10 were calculated by multiplying the mean T cell stimulation index (FIG. 25) by the percent of the tested individuals who had a positive response or a T cell stimulation index of at least two. The percentage of positive responders for each tested peptide were as follows: rCan fI: 89%, A0095: 43%, A0096: 43%, Construct 1: 64%, Construct 2: 73%, Construct 3: 82%. Comparison of positivity indices (FIG. 10) which measures both the strength of a T cell response to a peptide (S.I.) and the frequency of a T cell response to a peptide in a population of dog dander allergen sensitive individuals indicates that both N terminal (amino acids 1 through 65) and C terminal (amino acids 90 through 108) ends of the Can fI protein contain a number of T cell epitopes.

EQUIVALENTS

Although the invention has been described with reference to its preferred embodiments, other embodiments can achieve the same results. Those skilled in the art will recognize or be able to ascertain using no more than routine experimentation, numerous equivalents to the specific embodiments described herein. Such equivalents are considered to be within the scope of this invention and are encompassed by the following claims. 

1. An isolated protein or peptide having a T cell stimulatory activity of a dog dander allergen, Can fI, wherein the isolated protein comprises an amino acid sequence selected from the group consisting of: (a) amino acid sequence set forth in SEQ ID NO: 2; and (b) amino acid sequence at least 95% identical to the sequence set forth in SEQ ID NO: 2; and, wherein the peptide comprises an amino acid sequence of an antigenic fragment of the amino acid sequence set forth in SEQ ID NO:
 2. 2. The isolated peptide of claim 1, wherein said antigenic fragment comprises an amino acid sequence selected from the group consisting of amino acid sequence set forth in SEQ ID NO: 105, SEQ ID NO: 106, SEQ ID NO: 107, SEQ ID NO: 108 and SEQ ID NO:
 109. 3. The isolated protein or peptide of claim 1, produced by recombinant expression of a nucleic acid encoding the protein or peptide or by chemical synthesis.
 4. An isolated dog dander protein allergen, Can fI, produced in a host cell transformed with a nucleic acid comprising the nucleotide sequence of SEQ ID NO: 1, the coding region thereof.
 5. An isolated peptide of a dog dander protein allergen, Can fI, comprising the amino acid sequence of SEQ ID NO: 2, wherein the peptide comprises at least one epitope of said protein allergen, and wherein the epitope is consisting of a T cell epitope.
 6. An isolated peptide of a dog dander protein allergen comprising at least one T cell epitope recognized by a T cell receptor specific for a Can fI protein allergen comprising the amino acid sequence of SEQ ID NO:2.
 7. An isolated dog dander protein allergen, capable of stimulating T cells specific for a dog dander, Can fI, protein allergen comprising the amino acid sequence of SEQ ID NO:
 2. 8. The isolated peptide of claim 5, wherein said epitope comprises an amino acid sequence selected from the group consisting of amino acid sequence set forth in SEQ ID NO: 105, SEQ ID NO: 106, SEQ ID NO: 107, SEQ ID NO: 108 and SEQ ID NO:
 109. 